I'm not exactly thrilled with any of them at the moment.
Bill seems like a nice man, but his inability to criticise anyone (except Johndeep) is getting on my nerves. You are a judge for god's sake, that is the whole point!
Zoe very definitely has her favourites (this was really obvious in Maria too, I hold her responsible for the demise of the fabulous Abi). She is clearly none too fond of either Lee or Daniel (why god why?) yet thinks the sun shines out of Keith's backside. Bit of a show off and can be a total cow when she wants to be. On the other hand, I'm willing to believe she is good at her job.
Denise is very, very annoying. I'm not sure what she is bringing to this show other than her obvious assets.

The letching, thankfully, has stopped, but she definitely favours the younger contestants.
And that leaves John, who is probably the best of the bunch and who usually has constructive things to say. But he too is prone to favouritism (the championing of Ben and the constant bitching at Seamus).
I think that all the panel (except maybe Bill) have a better relationship with the younger Josephs and as a result are on their side. I guess this stands to reason, people like Lee, Daniel and Seamus are much closer to their own age (in the case of Denise and John) and are more confident in their own abilities and interpretations and less open to moulding and advice. I think this is why people like keith, Lewis and previously Chris B have had a relatively easy ride from the panel.