As a longtime vmware fusion user I have downloaded 4.01 trial. I encountered several serious bugs and problems within the first 15 minutes of usage:
General problems
- The "Upgrade Now..." option does not work. It just directs me to a site on vmware.com which contains this message: "Product data is unavailable. Please accept our apologies for this inconvenience."
- When I enter full screen mode in a VM when OS X video mirroring is enabled, the VM is minimized into the bottom left corner of the desktop - in this state I cannot interact with the VM - I have to kill Fusion alltogether
Problems with a Windows 7 VM:
- Totally corrupt rendering in IE9 - I had to apply "registry hacks" to fix the issue.
- Aero taskbar thumbnails not working in Windows 7
- Aero transparency colors slightly offset (darker than usual)
- Windows Media video playback does not work at all (blank screen inside the Media Player applivation)
I have a strong feeling that this is a rushed, not properly tested release. 
For the first time, I downloaded the trial version of Parallels (version 7) for comparison. It imported and started my Fusion VM without problems, and everything worked withouht a hitch as I expected. I am am seriously considering upgrading to Parallels 7 (especially the upgrade costs only $29.9 for Fusion users, which seems to be a better deal than $49.9 for Fusion 4).
Agreed. I don't do anything fancy. I just run Window 64 so I can run Quicken and Quickbooks pro. Performance took a big hit under Fusion 4. Fusion 3 was more stable and better performance than Fusion 4 by a large margin. Very disappointed with the upgrade.
Also, where are all these new features? I don't see all that much difference other than some changes to the interface and a big drop in performance.
Mark
Whatever. I made a quick search in my inbox, I've been using Fusion since June 2007 (1.0 beta4). I think what you see is the date when I joined to this forum (I joined recently only to express my frustration over Fusion 4...) But the issue is really not whether I am a longtime user or not, but the quality of this release, which seems subpar to me (maybe I'm wrong, or my Mac/VM has issues).
I wish Fusion good luck, but since my last post I purchased the Parallels upgrade for $29, and am happy with it. I still have my Fusion 3.1 license, so maybe in the future I'll change back. The only thing I hate about Parallels is its horrendous slightly less polished Dock icon, IMHO Fusion has a much nicer one. 
Downloaded and applied the update. All my issues have been corrected. So, time to take it out of the oven!