"Finally" I can tell a little about personal experience with DELL hardware and their service:
The issue: After about two months the motherboard of a DELL Latitude E5500 suddenly broke. That was quite clear after not getting any noise from the fan, HD and no BIOS message. Just the CAPS lock blinking. Called support hotline and explained what happened and what I already tried.
For the guy on the phone it took a longer while to identify my guess that it must be the motherboard, but anyway - better to be sure. The last thing to figure out was the particular main board type that was built in because there were two options. I didn't know in detail because it was DELL assembling the thing, not me.
To keep a short story short: "Next business day" to DELL really means "fix on next business day" - it's not just the first reaction on next business day. A guy from a partner company came to me / to the notebook with two spare boards and repaired the notebook. Other "local" support contracts expect that you bring in the thing to some shop in your more or less neighborhood.
It is really a pity, that the quality of computer hardware parts in general is not what it was 15 years ago. Unfortunately I see the reduced quality everywhere. Therefore a good service is essential nowadays.
Related post: The hardware, Going Linux, Ubuntu compatible hardware, The Dell Latitude 2110 and Ubuntu 10.04.1, The truth about hardware support.