I've moved over to 4.4 and been trying various ROMs, particularly Cyanfox and Neat. I decided to use ART, since that basically is where android is headed. I have over 200 apps on my phone and I haven't had any problem with any of them so far. I don't think that a normal user is really going to see a huge difference between ART and Dalvik. ART doesn't subjectively seem that much faster (and if your animation speeds are set fast enough, Dalvik can seem damn fast). Supposedly ART will give better battery life, but I can't verify that either. One thing I did notice is how much more space ART-optimized apps need. Fortunately, I had already remapped the PIT from 2gb to 4gb. If I hadn't done that, I couldn't use ART. My free space dropped from 2.3gb to 1.6gb. I think that is probably going to be a big issue in the future, as 4.4 (and likely 4.5, etc.) is supposed to be friendly to older devices and devices with lower RAM. I mean, if ART uses that much more space and you have a low RAM device, how many apps will you really be able to put on it? My S2 has 2gb device memory plus 16gb internal storage, which I was able to remap. What if you have, say 768gb plus 8gb, like an s-advance or other low to midrange phone? Like I said, that could mean not enough room to have ART and a large bunch of apps.