DOM engine and network lag are a much bigger bottle-neck for most mobile apps; where the lack of Nitro really hurts is <canvas>-based games, and specific CPU-heavy tasks (real-time photo effects, etc). For simple stuff like string manipulation, non-Nitro JS is still crazy-fast enough to be negligible in most cases.

However, I can attest that Javascript/browser memory leakage is a very real problem. It's manageable, but also very easy to screw up.

You can make it work, I can even have good animation performance with css3 on the iphone 3gs. Animating one or 2 items works well,

Things you need to be careful is too much animations at the same time & accessing and modifying the DOM while you animate, you need to "block access", something IOS does natively it seems.

But for Android that's another story, one device it's goint to be pretty good, on another it's complete crap and you need to deactivate animations all together.

Actually Nitro is not that bad. When you compare that to chrome on mobile, Nitro is same or better than chrome.

Try this out http://premii.com/hn - Hacker news webapp. I couldn't get same performance on chrome. Even Android browser performs better when it comes to animation.

I'd rather that than not be in the place where my users are looking.