No reason to be worried, it works just fine. Back up your data first to a sparseimage file using Carbon Copy Cloner to another drive if you're worried. I did the update on my Fall 2008 Unibody MacBook 13" and it went just fine.
It has flushed fine as well on mine but, I only get Max of 200Mb read and 100 write... I've tested in Windows 7 x64 bit with HDTune and CrystalDisk. What an I going wrong? My drive is x25-m 160gb G2 02HD
I know how you feel. I updated my Macbook Pro 17 and everything worked perfectly. I'm running OSX and Ubuntu 9:10. I split the drive 80GB a piece. For Ubuntu i'm pulling 220 MB/sec direct reads. Under OSX i benched the drive as approximately 200-205 MBsec on reads and 95 MB/sec on write.
Everything is working good.