I never had any issues with the 2 Dell Inspirons I owned, so I can't really comment on their after-sales service. However, I had an issue with my MBA's display and my MacBook's fan assembly and frankly, I hate going to the genius bar. It's always crowded, it's always a mess, and your appointment time is never respected (always have to wait 30 minutes+).
Also, you have to leave your computer there for 2-3 days, so frankly, not much different than "drop-off at depot" service you get from Dell.
My next laptop will probably be another MacBook, maybe an 11" air this time. However, I'm not fooled into believing the service and quality are somehow superior. Apple has good service, on par with the competition if you ask me.