Originally Posted by AidenM
Well, in terms of raw speed, it definitely seems snappier that dalvik. However, it takes longer to install APKs and every time you clear your cache be willing to wait for a while for it to re-"compile" your apps.
But using it depends on your apps - most of mine work with ART, so I use it. I know some apps like Whatsapp don't work with ART yet, so if you know your apps don't work don't bother to try it - you'll just get a bunch of force closes.
I haven't had a tablet since my TF700T which I returned after a few days because it L-A-G-G-E-D like nothing I have ever seen before.
I don't even know what apps to get besides the ones I have on my phone, so I'm sure ART won't be an issue.
I always install a ROM on my stuff because I like the extra customization I get, especially when it comes to the lock screen. Also, since I'm not a developer and don't understand that much about development, I trust that some of the ROMs allow snappier use and bug fixes from original Android. For instance, I have been reading everywhere that 4.4 is having some serious issues. I would hope these are fixed with a dedicated developer working on a custom ROM.