2007 MBP 3,1 is my main computer still. Upgraded to 8gb ram and an SSD drive. I'm on my third or fourth battery, second keyboard (cat, water, bleh), 3rd logic board (first two replaced due to Nvidia self-destruct bug), 3rd power charger, I replaced one of the hinges, and I've had to replace one of the fans. The DVD drive is dead, but I never used that anyway. Oh yeah, and my two-year-old son knocked it off a table so many times that the frame around the monitor is broken, so I have to hold the bezel together with clamps. Other than that it works great!
I still vastly prefer that style trackpad with button to the newer trackpads. I also don't like the sharp edge on current MBP/rMBPs in the middle part of the case where my wrists go :-/