We moved to Titanium from PhoneGap around 5 months ago - PhoneGap was just too slow for many options and did not support the low level audio functionality we needed. It may be better now though, but we haven't looked. Titanium has actually worked really well for us so I'm a bit surprised by so many developers having issues on here. Our app is coming out in about a month and is fairly large, with a custom UI:

http://www.groovydisk.com/