I have had eyes on Ibasso IT01s for a while now however when I saw these at 6k, I couldn't resist.
Comfort is great. They are light and stock tips are perfect, very comfy and don't fall out. They are fairly easy to drive out of my LG G7. Cable is light and thin, exactly how I like it. Thick cables feel cumbersome to me.
Now, to business - They sound fun, fast nimble bass to complement a clear midrange and non sibilant sparkly treble. The best thing is the timbre, which is realistic. I have been listening to Tin T3s, so these are a welcome break from the bright sound of the T3. Soundstage is decently wide with a little height. They are non fatiguing, I listened to them for 4-5 hours without any fatigue. I am happy overall.
Tip rolling is important here, people giving negative reviews need to understand that the source matters a lot. Give these a decent source, choose the right tip and they will shine!

Don't expect it bass heavy, use the soft white wide bore tips and use a DAC to unleash it's potentials. Burn-in at least 50 hours and experience the fast Bass with transparent Mids and polished treble.

The earphones have a very neutral inoffensive sound signature. Although the bass could've been slight better, but I think it's good enough for most. The best part is the treble response. The treble has the sparkles for most genres but it's very smooth and not sharp or fatiguing. I think overall this a good set for most genres. About the problem I faced with my unit is that the earphones are working fine but there is a huge amount of crackling sound when I try to insert them to my ears. The more I push the louder the sound becomes. Even sometimes if I move my jaw while wearing the earphones, it still happens. I contacted headphonezone for a replacement/refund for the product and they asked me to send the item to them. After receiving my item they confirmed there is no such issue with my unit. Now I have bought few stuff from headphonezone and never faced with any kind of issue before. This my first time that I have faced an issue and the service is like this. Fair enough it's not a big deal. Now I surely think twice before purchasing any item here. Never faced any issue with returns or replacements on amazon/flipkart. So yeah this is a disappointment.

Ill keep it simple. These are the best Dynamic Driver IEMs below Rs 10k. May be ER2XR are better below 13K range, but IT00 are really a surprise package at price well below half of that.
Pros:
Great Bass which is tight and detailed(Not Boomy or wooly).
Clean mids and Highs.
Non sibilant and yet very lively.
Good fit with stock tips.
They’re not power Hungry.

Cons:
Some people might not like them because these aren’t neutral or balanced IEMs. These are Fun sounding IEMs without a doubt.

Reviewed with: Custom Cable, Stock Ear-Tip (wide bore) & around 50hrs burn-in.

Before even beginning to write anything let me straight-off tell you that iBasso IT00 is NOT an audiophile IEM. Still you might wonder why I've given it 5-stars. Read on:

Where it is not Audiophilic:
-- Bass is a bit much for my taste. You can notice some bass bleed into the upper-mids. Thankfully the treble remains clean of the bass.

Where it is Audiophilic:
-- Treble is soft and smooth. This makes it non-fatiguing, but personally I feel it reduces the energy in metal and rock music.
-- Soundstage is wide but lacks depth.
-- Micro detailing and treble extension is awesome. IT00 brings out the smallest, hard to notice details in a track, despite all that bass.
-- Timbre is excellent. If you've ever heard cymbals / kickdrums in real life you will notice how close to real IT00 produces these sounds!

Comfort:
-- I literally slept for about 2hrs wearing these.

Why do I like it? (Meat of the review):
-- In spite of IT00 not following an audiophilic tuning, it tunes the sound in such a way that listening to music becomes a delightful experience!
-- Somehow listening to music feels almost pleasurable on these IEMs! This is the kind of IEM that will bring a smile on your face each time you listen to your favorite tracks.
-- If you are a hardcore purist who demands vanilla / neutral tuning, stay away from these!
-- But if you want to immerse yourself in your music collection while loosing track of the time, buy these!

These are warm fun sounding iems, but not for pure bassheads. In my opinion, requires 50+ hrs of burn-in to experience it's true sound signature.

Apart from sound signature, the built quality is good, could have been better. Mmcx Connectors are very difficult to attach or dittach to the transducers. 3 set of spare tips, a set of additional filter are provided with a hard soundmagic type carry case. Cable has L-shaped 3.5mm connector which is ok but can be bit tangly.

Overall a nice purchase for me as it adds a nice unique flavour to my collection of iems. Thanks to HPZ for nicely packaged parcel and quick delivery as always.

Fun & engaging to listening
I also own moondrop starfied & singot mt3. They also good but this product truly value for money at 6k.

BASS:
Unless youre looking at very high price points there is no doubt that delivering a clean, non bloated powerful sub bass without too much emphasis on mid bass is an extremely hard thing to do.
You always end up chosing between unclean but powerful bass or precise but anemic.

Here however the bass is felt not just heard and its fast and tightt and precise.
Bass guitar hums in you ear canal and sounds great.
Kick drums have the much needed punch.

This is the most satisfying bass Ive heard in an audio product, be it iems, speakers or headphones.(feel free to judge me ;) )

MIDS:
The lower mids and male vocals outshine upper midrange female vocals because of the bassy tuning of the iem the,vocals are completely clear just that someone who likes the vocals to sound more forward will feel that they are hiding with the instruments, this was fixed with some eq bg toning the bass down, and vocal centric songs sounded livelier this way.

TREBLE: Not the most detailed or sparkly but completely non offensive and easy on the ears.

INSTRUMENT SEPARATION:
Nice, its nice, no congestion felt for even when some songs get crowded with many layers.

SOUNDSTAGE: For an in ear at this price its freaking greattttt :D.

Recommended genres with default tuning:
House, trance, dubstep, techno pretty much anything that isnt live and vocal centric but it does fairly well with that too.

VALUE FOR MONEY:
For 6k I also have the ath e40 and ibasso competes well with that, even outshines it in some ways but is not as good vocally.
I will conclude that its pretty good value for money until I find something cheaper and better which is good at the same things that this IEM is. Which frankly speaking is a very very hard task.

HEADPHONE ZONE SERVICE:
The passion for sound shows, in the delicacy and thought with which each delivery is handled, I feel a great sense of happiness knowing that our country has companies that wanna give a taste of good audio to people. Well done guys :)

This IEM is a chef's kiss, if chefs ever got into cooking IEMs that is.