Ross Noble is for me the best I have seen in the last year or so, closely followed by Michael McIntyre. Though I suspect you wouldn't really enjoy seeing McIntyre two nights running whereas Noble is a brilliant improviser.
Eddie Izzard and Harry Hill are still brilliant.
Tim Minchin is fab.
Saw Dylan Moran recently and wasn't that impressed.
Saw Sean Lock too and wasn't that impressed.
Saw Jeremy Hardy and was a bit bored.
Saw Mitch Benn and if I had a gun handy I would probably have shot him.
I also saw Dylan Moran last year and was relatively disappointed. It wasn't bad, but I had expected it to be better.
John Moloney is still around doing the clubs, He's doing a stint at the London Comedy Store in a month or so, I'm hoping to get down there on a night he's on.
I've seen Jimmy Carr quite a few times, whilst I wouldn't necessarily enjoy his 'joke, joke, joke' style, he's very quick witted and brilliant in the sections when he talks to the audience.
Dara O'Briain is one of my absolute favourites at the moment - he mixes a bit of banter with well worked out stories.
I'm going to see Mark Watson next week, I saw him at the filming of Have I Got News For You last year and thought he was brilliant; I'll let you know next week I guess 
I also want to see Chris Addison. I've seen and enjoyed Jo Caulfield, Ian Coppinger and Reg D Hunter relatively recently.
Whilst it isn't stand up, my favourite regular comedy night out is seeing the Comedy Store Players - they do 2 hours of impro and are unbeatable! I saw Phill Jupitus guesting with them last week - it was grand 
Chris Addison was very good about 10 years ago, so I'm guessing he's learnt a lot since then.
Dan
I just can't "get" Dara O'Briain as a stand-up performer. It feels wrong. Having really only 'seen' him as presenter on Mock The Week, it feels like he's just playing at being funny, and isn't really ... a proper comedian. Or something.
Best I've seen, though I haven't seen many, I want to say Norman Lovett, yes Norman, he was very warm and had huge charisma. The audience loved him. Mitchell and Webb were good too but did not make me cry with laughter like Norm.
Worst, Nick Doody. He was toe-curlingly bad...ooh bringing back the feelings of watching him. My toes are curling at the mere memory of his badness.
And, although this is understandable under the circumstances, a pissed up Jeremy Hardy the night after or the night when Alan Coren died. I like to think that in a happier mood he may have been funnier and less of a twat. But I may never know.
ducky x
Worst I've seen was Rob Deering by quite a long way.