I have been using Parallels since it came out and have been very happy with it. I also have Fusion and am also happy with it. I have not had any problems with Parallels and do not understand why there is all these problems that are described here. I have been using a Parallels VM to run a video server app on my macmini for about 12 months with no issues at all. I have Fusion running on my Macbook Pro and it works very well also. I think maybe Fusion is a little faster possibly but it is only marginal. I have always been a fan of vmware products and run workstation on linux and that is why I have Fusion. If Parallels had not been so quick to bring out their product I don't think we would have seen Fusion in such a short timeframe. It is great to see the competition here so we get two great products.
Fusion is great if you want to run lots of different types of O/Ss both will run Windows great. I have no comment on game performance as I don't really play PC (Windows) games.