Hi
I currently have the Orbit 2, and at the end of March i've had it a year. For me its been a great phone (i had the Orbit as well), and the only problem that i've had with it is the rubber ring on the wheel is known to come off

. Mine did in November though i haven't got it repaired yet, as 1. you lose your phone for a week and 2. I've kinda got used to it without it, and its not that bad. So thats the only real issue I've had with it. I'm looking at phones now for in march and the Serra and Ignito, and SE X1 don't really grab me with excitement, and I've read lot about issues with them or the functionality. I've read there could be a new Touch Cruise (which is HTC's name for it) coming soon which hopefully O2 will do, which looks good
HTC - Products - HTC Touch Cruise - Overview.
It depends what your after from the phone at the end of the day, though it might be worth waiting a month to see what comes out.