I recently changed from Pre+ to Pre2 (exchange for almost next to nothing) & thought no point upgrading to Pre3 in a month time. However, I also bought a Veer for Mrs yesterday. Then, I was convinced that HP produces far better hardware than Palm had ever done.
From the look of it, bigger screen, fast processor & better hardware will push me upgrading if
1. Price @ £350 in the UK
2. Battery life improves.
Otherwise, I wont switch until webOS 3 upgrades.