Keep in mind this is the 5.0x Safari/Webkit and not the current 5.1 that is truly Intel only.
I ran an available Safari update on my Sawtooth G4 about 4-5 days ago that updated it to 5.06. My point is that even Apple released this and it would be more stable than nightly builds.
I found the Safari 5.05 release from Apple less stable than the last PowerPC Webkit build and I normally run both simultaneously due to running multiple websites/blogs on the same sites and the need to separate cookies. I will extensively check out Safari 5.06, but I seriously doubt it will improve performance on PowerPC machines, but maybe stability.
Now as for Camino vs. Safari on Acid3, I've never used the test and I don't deal in George W.'s fuzzy math.
The facts on the ground speak for themselves on all the websites I normally go to including Youtube and Facebook, among others. An optimized G5 Camino build is significantly faster than Apple's universal binary build of Safari. That's not my opinion, it's just reality. Now if I compared the standard Camino build vs. the standard Apple Safari build, well maybe it would be different, but I think I just found my browser of choice now that Apple is discontinuing Safari for PowerPC and I like the speed.
And as for the suggestion of using the HTML5 version of Youtube instead, everything I've read about HTML5 vs. FLASH has proven that HTML5 videos are larger, so I doubt that would be that much of a difference and last I checked there is no HTML5 version of Facebook.
Finally, there are several things that bother me most about this whole issue...
#1: Apple has made no announcement to its customers, yet continues to update Safari for Windows XP.
#2: Webkit.org made no official announcement of dropping PowerPC support in Webkit either, at least not on their main webpage.
#3: Webkit updates actually BRICKED Webkit for PowerPC users when the trunk change happened without warning. That's just insulting to my intelligence and makes me want to scream, "What AHOLES!"
PS: And even Macrumors.com runs faster on an optimized G5 Camino build than on the latest Safari. If this works as well on a G4 (which I've yet to test), I'm switching some relatives and friends away from SAFARI (people who only use their computers for webmail as that's also faster on Camino than Safari).