[krishan711]

I've been using it on my main device since July and haven't had any of the problems you've metioned :S The only problem I have is the Settings app ocasionally crashes when I try to setup a new wifi connection. But I don't do that nearly often enough to be upset about it. That said, I haven't noticed any improvements. It seems the same (speed / performance) wise as 4.4 on my N5.

[kolev]

Yes, even on 4.4.4, there was no noticeable difference between even ART and Dalvik. Again, that's why I wanted to use it daily as labs are one thing, but real world is often quite different.

[microtonal]

Yes, even on 4.4.4, there was no noticeable difference between even ART and Dalvik.

On what hardware? I did not notice a difference on my Moto X. My Moto X is in repair now and in the meanwhile I have been using a Moto G. On that, I definitely notice a difference - app starting and multitasking is a whole lot faster with ART.

[kolev]

On Nexus 5 (Android L preview is only for Nexus 5 and 7).