I bought Macdrive 7 a while ago. It worked on XP, but it really slowed down boot/shutdown times. It also caused Windows Explorer to become unresponsive sometimes. I tried the updates to no avail. I gave up and uninstalled it.
Now that I'm using Win7 RC 64, I thought I'd give Macdrive 8 a shot. I tried the beta (v8.0.0.129). It could see the files on my HFS+ partitions, but it couldn't read the files. It kept giving me read errors. I uninstalled that one too.
With the release of Macdrive 8, I decided to give it one more shot. I've been using the trial for a couple of days (v8.0.0.148). It's working very smoothly so far. I can get version 8 for cheap since I own version 7 already, but I'm going to hold off until Boot Camp 3 is officially released before I consider an upgrade to Macdrive.