I'm torn between this and the Vigor. I am very loyal to HTC after owning the Incredible since its launch date... that was just an all-around solid phone. I also shy away from huge phones... I would rather have a sleeker phone.
My 2-year upgrade is Dec 29th (although I can usually talk them into allowing it earlier), and I still have my last 1-year upgrade discount available right now. I recently cracked the glass on my Incredible while backpacking, so I'm going to try and replace it, but I think it's time to upgrade this fall.
I'll keep watching, and probably won't make a decision on the Vigor until I see the official specs of the Prime. I have heard bad things about Samsung, but mostly that relates to updates, which I understand isn't an issue here.