So, I got me a BenQ E2220HD
to go with my shiny new computer. I've connected it with an HDMI cable to my HD5870.
The monitor claims to be 1920x1080, but when I try and set that resolution I get black bars surrounding my picture, and some ugly squashing too. 1680x1050 on the other hand fills the screen nicely, but it's stretched out a bit in places. Far from ideal. Also my monitor pops up the OSD and advises me to use 1920x1080 whenever I switch away from it.
Drivers on the graphics card and monitor are up to date (I installed the monitor drivers even though it's plug and play, to see if it fixed it. It didn't.)
The internet seems fairly useless at providing a solution, I've found a few other people with the same problem but none of them managed to solve it and survive to post how =P