If you're used to consoles on a 1080p TV, you've got the gist of what low resolutions look like in games. I'd take playable settings on Ultra at a lower res vs. lowering the eye candy to medium or low on a high res. Honestly I don't see much difference btw my monitor's res and 1080p. 1200p is pretty sick tho - mostly because of how easily aliasing can be cleaned up.
I don't have a problem with my lower res - aliasing is a concern, but FXAA and MLAA clean it up pretty well, and I don't mind a small amount of blur. Plus it means I can run Ultra on every game with a $200 GPU vs. $300+ GPU for 1080p or higher.