Optiplex GX270's (in addition to the 280's you talked about) all have faulty capacitors in their motherboards that make them go bad right after the warrantee expires. I had to deal with them at work for a while.
Some other infamous creations with the Dell logo include numerous Pentium 4 Inspirons which overheated due to cheap design. A friend of mine has one and it's such a piece of cheap junk. OP, yeah, and I forgot to tell you all about those lovely exploding batteries from Dell too! Oh, and guess what? Dell knew about all this but still sold that hardware. Call that honesty!
I'm not buying a Dell. Ever.