Dinny,
I use a a 24" Asus as an external monitor for my MBA. I will have to agree that it does not have the pixie dust of the Apple monitors but It works very well considering I could buy five of them for the price of the Thunderbolt. Besides my MBA does not have a thunderbolt port. Like Dan however, most of the time I just use the built-in display, unless I have a big-ass spreadsheet.