I've read very good reviews of Dells high end, mobile graphic workstations, and high end gaming laptops, as well as their 24" flat screens......
As far as their entry desktops..... I always assumed the reason you see more Dell ad's on TV than ANY OTHER MANUFACTURER, as well as "product placement" in SciFi channel shows (I think "StarGate" uses Dells) --is they are generally aimed at "younger consumers" --and evidently Dell requires more "first time" buyers (ie, the quality is such that they don't have so much repeat business, or customer loyalty).... but that's just a guess.... but MAN they spend a fortune on TV..... I bet if you buy a $500 box from them, $250 of it is marketing..... and it cost them $100 to build and ship --from China.
So... If I was wanting a desktop.... I'd go with the "read reviews", buy the parts you want, a book and a screwdriver, and build it yourself... that way you KNOW you got the parts you specked --not parts Dell got a good price on that week
If you're considering a notebook.... or looking for good deal on Dells --like their coupons-- you might want to look at
Notebook Forums They have a section on Dells, as well as a section on whatever manufacturer is currently offering a discount, when and for how long..... you can pick up some really good deals that way
If you don't want to build a desktop yourself.... perhaps consider going to a local shop and have them build you a machine to your specs.... and get warranty on it... then, if something dies (and stuff does --trust me) you don't have to ship it around the country.... you just drive over and hand it to them and say "fix it".... I'll be back after lunch.