A while back, I took the plunge and rooted my Transformer Prime tablet. Found an Android 4.2 (Jelly Bean) ROM to install and installed it along with a new recovery ROM. Worked pretty well and made the tablet fun to use again.
The Galaxy S2 got the Cyanogenmod treatment with CM11, but for the past few months, ROM updates have been relatively infrequent, and there were no signs of Android 5 (Lollipop) ever making it to the S2.
With Android 6 (Marshmallow) being pushed out to phones, I decided it was time to bring the tablet and S2 a little further into the future. The XDA Developers forums is a good place to find builds of new ROMS for all kinds of devices. The Transformer Prime got the KatKiss 5.1.1 ROM along with a fresh TWRP recovery ROM while the S2 got the Candy5 5.1.1 ROM as well as the TWRP recovery.
The ROM install on the S2 was pretty painless, and seems to be running pretty well so far. Thought the S2 might have some issues running Lollipop, but so far so good.