It depends on the situation and the channels you use.
A mate just had a brand new power adapter shipped for his notebook that is 7 days from expiration of warranty. They even provided a box for him to ship back his old one for testing.
I've had no problems but that's because I've had no reason to call them. My laptop is fine!
As for the purchasing of computers from ANY large PC company, you're going to get pwned... You should know that... It's not dell specific...