I have installed every service release to date including the figure updaters. But I am going for a fresh install. The reason being that I am not sure it is really humanly possible to track all the changes in the betas and SR's and make sure that every previous fix is overwritten.
In addition I have had so many really bad crashes and lock-ups in the earlier releases that I am not sure that there are not corrupt files lurking in my P5 folder that lie outside of the scope of SR3.

My strategy is as follows.

1. Make a copy of my Runtime Folder elsewhere on my system.
2. Completely uninstall P5 and wipe residue folders.
3. Defrag my Poser resident Drive fully.
4. Install P5.
5. Install SR3 and figure updaters.
6. Add the folders from my second saved runtime copy to my new P5 runtime (with the exception of the updated P5 files) and then wipe my saved second runtime folder.
7. Defrag again.
8. Cross fingers and run Poser SR3!

regards
STORM