I've run smcFanControl on every single x86 Macbook Pro I've ever owned, as the MBP has always been a hot machine. For some reason, the default SMC settings leave the fans on a very low rpm setting (with an occasional massive spike up to 6-7k), so running them at 3k rpm helps the temps be a bit more consistent (mine idles around 45 C on a 2.8 GHz Nehalem 2010 MBP running the NVIDIA discrete GPU exclusively).
Now it is well known that Intel and most OEMs use the crappiest of crappy thermal paste for the CPU heatsink, so replacing it with one of the silver microbead compounds does make a difference. Apparently this is a big issue with Ivy Bridge, where the CPU die mount is covered by a metal heat spreader and is awash in crap thermal paste (making Ivy Bridge chips run hotter than they should). But completely taking apart a MBP, removing the CPU/GPU heatpipe and then removing the metal CPU heat-spreader to apply better compound is not a trivial task. So really think hard about whether those 5-8 deg are worth the ass pain of potentially damaging the CPU die.