One downside is that you can't resize it while it's mounted (at least not when I last tried), so it's not ideal with LVM.
Speaking of which, I need to make several of my GNU/Linux partitions smaller to free up some space for *cough* that other OS, particularly as GNU/Linux is compact compared to the bloated other OS (and also cos it doesn't have as many games). What utilities could I use for this? I have used Partition Magic in the past which had a nice GUI and meant that even a fool like me could do it without fscking up everything. I use ext3 as well.