+1 for "normal", non-curved screen.
I remember from one of the hands-on videos floating around that Fxtec might change screen manufacturer, so maybe there is still a chance (however slim) that we might see a flat screen with normal edges.
Flipping the screen up to reveal the keyboard while the screen is on seems problematic if the edges are curved, feels like I might accidentally open an app or change something. But then again I have not tried the phone so it might not be an issue. From the videos I see a lot of unintentional screen touching though... Fxtec seem to have made the flip-up mechanism spot-on, so it would be a shame if the curved screen made using the device less user friendly.
Durability is another concern, but again time will tell if this is a problem at all. Might be sturdy as hell who knows :)
Price... I don´t know if a curved screen drives the price up or not, but if it does I wonder how many potential buyers would rather have a flat screen and a somewhat lower price. Heck, for me they can use the flat screen and keep the money saved themselves since I really want Fxtec to succeed!