For your consideration:
Heres 1280x800:
And heres it with the Dynamic Resolution Mod scaling to 75% of 1280x800:
And 50% of 1280x800:
As you can see, looks terrible (except for the UI, which is why you'd use this mod, however...)
Heres 720x540 (I've fixed the mod showing the wrong resolution in a
later pic)
And 720x540 without the options:
In my opinion, except for the pretty much un-readable UI, the 720x540 screenshot looks much better than the 1280x800 scaled (one of which is higher resolution than the 720x540! Compare the two side-by-side, tabbing back and forth really lets you see how blurry the scaled options are.
And heres the mod showing the right value for the resolution (sorry the new pics dont line up with the older ones!)
http://i.imgur.com/pkZaKaa.png
http://i.imgur.com/rai49UG.png