I used to have Netflix in the U.S., and used it heavily. It was a great service, especially their streaming offerings.
When I moved, I looked into Lovefilm, and just hated it! Their streaming options (which is what I'm most interested in) seemed pretty limited, and it seemed that anything worth watching cost extra. Not only that, but their UI was horrible! Rather than linking to an entire season/series, they listed every single episode separately. So bad! So, I never signed up.
From what I've heard from people at home who still have Netflix, their older/niche streaming options are being cut down. What I've read online suggests that this is because they're trying to make deals with rights holders to get more new releases, faster. But the rights holders still haven't woken up to the fact that their market is changing, and are playing hardball with all the streaming services. And when it comes to non-U.S. services, the situation gets even worse, which is part of the problem Lovefilm has always had.
So, I'll definitely check out Netflix UK, but I'm worried they'll be hampered in the same ways Lovefilm has been. Although, even with the same offerings, as long as Netflix UK uses the same UI, it'll be better than Lovefilm.