I installed Parallels Desktop RC2 on my 2GHz MacBook with 1GB RAM this evening. After going through the simple setup procedure, I installed Microsoft Windows XP SP2 and then a couple of apps (including some beta release software). Everything looks good so far.
I use Microsoft Visio and Microsoft Project. Since, they are not available for Mac OS X, getting them on my MacBook was a good reason to install Parallels Desktop RC2. I installed Microsoft Project 2007 Beta-2 and Microsoft Visio 2007 Beta-2. I was able to to more-or-less comfortably check my email on the Mac OS X side (Thunderbird) and surf the web (Firefox) while Windows XP installed these applications. Application performance inside of the virtualized Windows XP window seemed pretty decent too. For yucks, I installed Civilization II (a decade old game that consumed a lot of my time years ago). It seems to run ok too so far. I was concerned that a MacBook with a mere 1GB RAM would not be a comfortable fit for running Windows XP. But, things look ok performance-wise. My only MacBook regret now is that I should have upgraded the hard drive to a larger size so I can comfortably install other virtual machines (Fedora Core 5, etc.).