Palm Prē very closely. I don't think I've ever been this excited about a piece of gadgetry.
(In case you've not seen it yet, here's a pretty decent 26-minute demo.)
At CES, it was mentioned (probably in passing) that information about the UK launch of the device would be announced at the Mobile World Congress in Barcelona, which has been running since Monday. I'm checking the "gadgets" folder in my Google Reader feeds every 20 minutes to see if anything new has been announced, but so far there's been nothing substantial; a few new features, some clarification on what it can and can't do (so far), and the first chapter of the textbook on developing new applications for its webOS operating system.
Rumours abound about the carrier that it'll eventually land on in the UK. The American version of the phone will be on Sprint, while a lot people seem to think that Vodafone will get the UK contract. The strongest evidence is that the phones at the MWC were running on Vodafone's network, but I thought that they would be too concerned about the impact on Blackberry Storm sales (and now, the HTC Magic) from the Palm Prē - which seems to have a buzz about it bigger than any I can remember other than the iPhone.
The MWC ends today, so there's only a few hours for them to announce the UK carrier - if it doesn't come out of the congress, chances are it'll be long after the (still un-dated) American launch before I get any idea of when I'll be able to pick one up.