my first mbp was the first gen unibody. i'd give it an 8, mostly because it had more backlight bleed than i'd have liked. i say 'had' because amazingly the bleed went down over time, to the point where it is next to imperceptible, and yet the screen as a whole is still very bright. i had the superdrive and a bulging battery replaced under applecare, but the repairs were quick and painless. the 9400m occassionally flickers a row of pixels, but never anything major, and i use the 9600 most of the time anyway.
i recently got a 2011 mbp, and for the month i've had it, i'd be very tempted to give it a 10. the speed boost (almost 3x over the 2008) has been great for my work, the temps are good, runs silent unless i'm pushing it with a render, and the hi-res screen is great. of course its long term reliability remains to be seen, so a rating at this point probably doesn't really mean much.
overall i'v had pretty good luck with my macs. i still have a powermac g5 that never had a single repair. its rarely used, but when i do have it on, it runs the same as when i bought it. likewise the 2008 mbp runs as good or better (backlight improved + ram upgrade) than when i bought it, and for casual computing tasks, i wouldn't know the difference between it and my new machine.
