1) I’ve started maintaining Optiboot for the Arduino team.
2) There is now a version with a number of significant fixes and upgrades, compared to either the older (“v3”) downloadable version, the google code source version, or the version that has shipped with Arduino (on boards, and in the 0022 distribution.) http://arduino.cc/forum/index.php/topic,64105.0.html This is “shipping” in the “Arduino 1” release candidates (I’m not sure when it will start showing up on hardware.)
4) However, It hasn’t been tested on any of the SparkFun “Pro” arduinos or other versions (I don’t have any!)
5) We’ve also revived the optiboot google code project: http://code.google.com/p/optiboot/ In theory, source updates (especially those that don’t affect Arduino ofifcial platforms) may appear there first, but the general idea is to keep the distributions in sync.