In short: Don't do it.
I've wasted half of yesterday and much of today getting my Late 2008 MacBook Pro back into shape after installing the 10.7.5 update.
Worst of all: My fink installation won't update, which means re-installing XCode and then re-installing the command line tools, which is so slow that I have time to write this.
My MBP booted 10.7.5 once, and then thereafter only gave a kernel panic on boot. I had to re-install 10.7, and then download the 10.7.4 combo update and install that.