to the harddrive guy, I myself got a seagate momentus 7200.4 looking at some websites it is ridiculously fast, but does use a bit of power. I'm getting a backup drive, likely the western digital above, it uses less power than the seagate, but is a tad slower.
One factor that hasn't been mentioned is the the MBP is fully 64 bit cabable both kernel and EFI
the MB are purposely crippled to only support a 64 bit EFI and can only run a 64 bit kernel with a fair amount of hacking.
It doesn't make a huge difference as they both run 32 or 64 bit software fine, the only difference is the kernel a 32bit can not support 64 bit kexts while a 64 cant use 32 bit *shrugs* not a huge difference, but something worth noting I think.
the backlit keyboard is great, I type without looking too, but sometimes at night, if you don't have your hands resting on the home keys 100% of the time it's nice to have the lit keyboard just to place your fingers, then type away, plus it just looks awesome. It is true the screen CAN light the keyboard but at night i tend to lower my screen brightness, and then you can't see the keyboard so just turn on the backlight, brilliant! I've even just turned off the screen and turned on the keyboard backlight to type!, it's useful for class sometimes if theres a powerpoint and the room is dark, you can turn off your screen and not disrupt other, and see the keyboard perfectly fine (typing without a screen is a completely different story though haha)
the other difference is the SD and firewire
like someone else said the expandability to 8gb of ram(really only useful if running vms they will run fast but your comp still gets pretty hot)
I have an alum MB and i love it, the backlit keyboard, aluminum, glass screen. I really think the keyboard alone is worth the 50 bucks, even if you THINK you won't use it, you'd be surprised how useful it is.