FYI, my slider doesn't open much, but it does slide just a little bit... The only thing about it that bugs me is that if you open and close the slider, the phone turns itself on, and you could dial in your pocket.... I think that's happened once in 6 months, however.. It's not a huge deal.
I understand where you're at... I've been debating getting a treo for a while, just to play with it. One of my good frienRAB has a treo 650 and she LOVES it (hers isn't on cricket).
I don't think you can go wrong with the 700wx or the 6700. BOth are great phones. LIke I said earlier, it's all about which you prefer, and if you have the skills to mod one, or someone willing to mod it for you.