Is ART on Lollipop the same as on KitKat? I have issues with skype on my KitKat phone with ART enabled. None too serious, but launching is very slow.

Will the same issues plague me on Lollipop when my phone gets it?
No. ART on KitKat is not ready for production use, and shouldn't be enabled unless you want to test apps you're developing (and even then, you probably only need it to test native code). ART on Lollipop is the finished, production version.