Its brilliant stuff so long as you dont rely on it as a permanent repair. Thats why its generally a jazzy colour so when you regularly examaine your tyres
you'll spot it.
I know a fair few folk (mainly bikers) who swear by it and could tell you stories all day.
I'm also aware of a vehicle fleet that uses it and they run everything from vans to high performance vehicles with it fitted and no problems, completely the opposite in fact.
To avoid balance problems use the correct amount for your tyre size and be patient because when you first put it in it needs to find its own level as it spreads and will feel out of balance for a few miles.
On a personal note I put it in the tyres on my last caravan as a bit of a confidence ting and one benefit I found was that the tyres held their pressure far better. I dont mean anything radical just in the 6 months it was in I never had to pump them up
You can now get the goo that washes out with plain water (not all types used to) so it'll clean out and the tyre can be repaired as if it wasnt there.
You cannot use it with powder balancing if you have that fitted, for obvious reasons, you'd just end up with a useless sludge sloshing around in the tyre
Hope that helps.
I'm not any kind of expert but on a n other forum a very anal tyre fitter had a downer on the stuff and the more I researched the better it looked and his anti argument fell at every hurdle. Thats other than DONT treat it as permanent repair, its a get you home save the tyre deflating at an inconvenient point measure.