I use IBM, but see my technically-oriented colleagues use IBMs, Dells and Toshibas in equal proportions.
I like the Sony laptops, but I sense from discussions with their owners that service is a bit more of an ordeal for them.
Relative to dealer support, I have concluded that in the U.S., there is essentially none for IBM laptops. The typical dealer response is "Uhhhhhhh . . .". When there is a problem you call IBM, they express a special box, and you send it in for about a 3-day turnaround. Take it to a dealer and you are looking at a week or more in my experience. (I think a lot of the dealers just send them in as well.) So, look for these types of express-shipping-based service options as well. (And do your backups!)
[ 29 October 2001: Message edited by: Eboy ]