I've been through 12x 15" 2.4ghz mbp from last years model "merom" and 8x 15" 2.4, 2.5, 2.6ghz model of the "penryn" this year and all of them had the left speaker sizzling noise issue when the magsafe is connected with after a sound has played, magsafe green light not coming on sometimes, 1 had vertical led light issue, all of them had some sort of yellowish/beige tint at the bottom, and the 15" mbp generally felt more clunkier in performance and not as fast as the 17" mbp (maybe because the 17" mbp has a much bigger and more efficient heatsink), and finally the headphone jack via external speakers or headphones made hissing noises.
I've been through 2 17" mbp earlier this year just when the hi res led 17" mbp was released I bought the 2.5ghz model and compared to all the 15" mbp it ran overall much faster and I know what to compare it to as I had the mac pro desktop that ran as buttery smooth.
I ended up selling the 2.5ghz model 17" hi res mbp because I wanted a mba (since I already had a mac pro desktop) and once I got the mba, it was just too slow for the $$ so this is where my quest for the perfect 15" mbp and since then I returned up to 8 and finally ended up buying the 2.6ghz 17" mbp and sold the mac pro and do not regret it at all.
Anyway especially connected to my 23" and 30" acd the 17" mbp felt and was much closer to the buttery smooth osx that I was used to on my mac pro. The 15" felt like it hiccuped using expose and multitasking where this wasnt a problem with the 17" (felt more like a desktop speed).
Everything loads much faster and I've never had any image load slow on the 17", actually it loads alot faster. Also I had all the same specs on all of the 15" mbp that I had, I have a hitachi travelstar 7k200 that I installed on each of them with the 4gb of ram as well.
One interesting thing is that after 3 months and using my 17" hi res mbp, it feels like a 15" mbp again. I completely forgot the footprint of the 15" mbp and whenever I look at the 17" or pick it up, it feels small and I keep thinking its a 15" mbp with a higher resolution and bigger, clearer, louder speakers.