Using Win4Lin, even a 2 GHz Pentium 4 is dropping 25% of the frames for the "large" trailer size. The playback was even worse for the "full screen" size. Of course, the normal installation of Windows 98SE did not drop any frames, and playback was smooth (and the same was true for a 500 MHz Pentium III from Falcon Northwest). Once again, Win4Lin has turned our shiny, new Pentium 4 into a sub-500 MHz computer! To be fair, Win4Lin is not dropping any frames for the two smallest trailer sizes, and even for the "large" size, playback is decent. Considering that Linux does not have a native way for viewing QuickTime, any frame rate above zero is an improvement.
Graphics professionals should probably stick with Windows because they will notice the difference in performance. For games, I would also stick with the dual boot for now. While some titles are available for Linux, most still require Windows. QuickTime using Win4Lin, while good enough for playback at low resolution, is not going to cut it for 640x480.
The kernel release schedule is also something to key your eye on. With Linux, it is very important to have a kernel that is up-to-date, lest the script kiddies use your box for denial-of-service attacks and other forms of badness. Since Win4Lin is working at a very low level, you need to be using one of the "enabled" kernels that can be downloaded from the web site. NeTraverse has just released enabled kernels for Red Hat Linux 7.2, so it looks like they lag behind the distributions by about two weeks. However, their most recent patch for the source at kernel.org is for the 2.4.9 Linux kernel, originally released on August 16. They really could be doing a better job on their release schedule for patches to the "official" Linux kernel.
Finally, for those of you who have been waiting for office applications to materialize before giving Linux a try, wait no more: Win4Lin is just what you have been looking for. You really can use Word, Excel, and PowerPoint inside Linux, and with a GHz+ machine, you should not really notice any performance problems for these applications.