Hail, Heim!
I don't PvP so my feedback may be irrelevant, but I speak from the side of the fence that loves the new client (KR, Kingdom Reborn) and still very much enjoys UO (10 years and counting). It has gone through many changes over the years, and many shards these days are sadly ghost towns. I had moved to Lake Austin last year to play with the UOForums guild and had a fantastic time. Most players from the guild moved on, either to other games or back to their "home" shards, which is what I have done recently. I'm back on Atlantic, where I spent 9 years. My brother and an old friend have both come back to the game this year, and with that I'm back to having a blast.
In my opinion, it's more about the people you're playing with and the interaction and camaraderie than anything else. If you enjoy the company you keep, anything can be fun.
Like Bruno said, there's a 30 day free trial you can use to start up a new account and see what you think. If you don't like being a newb, you can buy "advanced character tokens" at
http://www.uogamecodes.com/ that get your character instantly to a decently playable skill set (if reactivating an old account isn't an option).
Whatever you decide, UOForums is a good community to hang out with