Need a new phone...any suggestions?

I (rather stupidly) switched my old Samsung G800 for a cheap and cheerful LG Cookie Fresh about 6 months ago and I'm starting to get fed up with some performance issues I'm having, along with an absolutely rubbish phone camera. I would like a new smartphone and was wondering what the best ones are. As far as features are concerned I'm not particularly fussed, however I would like a good camera and probably Wi-Fi, Bluetooth, a 3.5mm headphone jack and all the rest of it would be good for the rare times that I don't have my shiny iPod Touch handy. What I really want is a usable UI combined with smooth performance. I was thinking mainly of going either HTC (mainly a design choice here: I like the looks of most HTC phones and the Sense UI looks very slick) or Samsung (because I've had a couple of Samsungs in the past and liked them quite a lot). My budget is around AU$600 which, on eBay gets most of the latest Android 2.2 or WP7 phones on the market at the moment.

Thanks in advance.