Alright I finally got v5.1 installed last night.
Verdict:
So far it's been very stable! I had one issue with Titanium where it wouldn't restore a particular app, so I unticked that app and restored the rest just fine. I hope everyone did a fullwipe before installing v5.1, it's very much recommended. I restored all my sms' perfect as well. Not sure where all these issues are coming from.
The issue with restoring one app at a time sounds like you haven't installed the licence key from the market. I'm not sure where you guys are finding FCs but I haven't come across anything just yet (I'll keep updating the first post though).
In summary, I'm sticking with v5.1 for now. The battery seems a lot better than v4.1 and it's overall more stable. Also, there's a few new nifty ICS features in LPB like swiping contacts to call/message
Edit: I've also updated the OP with new info and pictures for v5.1!