You're dead on that many people who like to compare brands forget that some brands have different notebook lines which include separate warranties and service. I'm a prospective MBP buyer who currently has a Dell Precision M4400 and has owned consumer inspiron models in the past.
The level of service is day and night. With the Inspiron, it took forever to get through on the phone, the build quality was average, but the notebook was cheap in price. This Precision I'm using, when calling I often go straight to support (and usually some one in the US, instead of a Panamanian I often get when calling the inspiron support line). The precision model came with a 3 year warranty. I've had to replace the keyboard over something minor once and Dell Business was quick to send parts over w/o cost, and a prepaid box to send the old keyboard back.
Some nice things about this Precision M4400 is that it came with both a vista and xp install disc, something missing in many brands nowadays (including Dell's other line up). There's a huge plethora of ports, express card, 4 usb with 1 combined with e-sata, displayport, pc card slot. the m4400 is similar to the E6500 but has a sturdier magnesium lid. the build quality is sturdy and the Keyboard is close to Thinkpad levels (but not quiet). I certainly enjoy typing on this much more than my past Vaio SZ (one of the worst keyboards I've used). Driver and bios updates are frequent. The screen is very bright, brighter than the 2009 MBP 15" glossy. The 9 cell extended battery gives me about 6 hours of battery life at best and the video card (FX 1770) (while not optimized for gaming) is good. I wish i got the RGB LED screen but settled for the regular white LED backlit one. Upgrades have been easy since the bottom is one giant panel.
But there are some things I don't like about it either. It is heavy. its not the thinnest 15", but the power supply that comes with it is huge and bulky!
The notebook also had some audio stutter which was not really resolved until the release of a more recent BIOS. The screen, while being super bright, has a blue-ish tint.
I'm looking to replace this M4400 with an MBP because i need something lighter and I realize I don't game so much anymore on a computer. I also want to learn app development so a Mac will be necessary. It also helps that I really like the unibody design of the Mac.