Don't know about all-in-ones, but Vostro in a desktop is a budget model with a cheap mobo. Still probably OK for general computing.
I had a vostro 490 (or 460). BOught it 2 months ago. Can't support 3 monitors though they said it would. It's not a very good computer. If you are going Dell, get an optiplex. Same price for same specs. Better PC. Macs are tonka trucks compared Caterpillars for real work (work that involves numbers and not feelings).
Wouldn't recommend Optiplex line either... they also use a budget mobo but are priced higher. If you want a quality Dell, get a Precision T3500.
I'm not looking for quality per se. I like the 23' screen. I want something small, cordless and easy to move. I never thought I would ever want to buy another desktop again, but my eyes are getting sore staring at tiny laptop screens for extended periods of time. That is why I'm looking into the all in one machines. The I-mac is nice but might be over kill.
http://www.dell.com/hk/en/business/p/vostro-360/pd For a non trading recreational machine, looks fine to me. I prefer windows over Lion.