If you're using a utility like Jonathan Pepin's CoreDuoTemp v0.6 or Dr. Marcel Bresink's Hardware Monitor 3.6 to keep tabs on your CPU temperature you'll be disappointed to learn that Apple's recently released SMC Firmware Update breaks these applications on the MacBook Pro.
Apple's suitably vague on what, exactly, the SMC Firmware Update actually does other than saying:
The SMC Firmware Update 1.0 is a System Management Control (SMC) firmware update for certain Intel-based computers, including iMac (Early 2006), Mac mini (Early 2006) and MacBook Pro (15-inch) computers.
CoreDuoTemp relies on InCrew's SpeedIt kernel extension to get its information which is apparently broken by the SMC Firmware update.
According to Information Week the new SMC Firmware update reduces the operating temperature of some user's MacBook Pros:
Although Apple said that the update was to "System Management Control (SMC)" firmware, it was up to MacBook Pro (MBP) users to figure out that SMC is the specialized controller that manages thermal and power conditions, and is in charge of running the portable's fans.
Within hours of the update, users began reporting that the update seemed to increase the MacBook Pro's use of its fans, and using diagnostic tools, claimed that their machines were running up to eight degrees cooler.
"The fans are now working like they should," wrote another user, dubbed 'interval,' after he/she had installed the update. "Although the computer is much louder when being taxed, it's much much cooler. In fact, the area above the f-keys is just warm to the touch because the fans are actually forcing the air all the way out of the machine."
I just installed the SMC Firmware an hour ago so I can't really comment on its performance yet, but any prospect of cooling my MacBook down sounds attractive to me.
What has your experience been with MBP temperature? Have you installed the SMC Firmware yet?
UPDATE 2006-0519: I removed part of this post containing InCrew's comments as they were relating to the previous Firmware update, not the SMC Firmware.