1) If you mean the grey apple in exchange for the happy Mac, yes, that image can be changed... though you'll have to Google for how unless someone else suggests someting. If you want to change the actual progress bar load screen, I'm not so sure. I'm sure it's possible, but I've never read of anyone doing it.
2) Not for me. Have you tried re-applying the combo updater and doing the standard disk checks? Also, do you have anything else installed (3rd party additions, hacks, etc) that it might not be liking, perhaps?
Have a look at MacFixIt--they have a tip about deleting some specific low-level cache files that may also help.
(Though I have to admit, being Badass Slow™ sounds so cool I almost want it to happen to me...)