Last night I installed the upgrade. Took four hours.
After installation, 7 gave me several points of pain, most of which I solved in under an hour, fortunately:
100% CPU Usage
7 was running very slowly, and I finally found it was due to the CPU being run at 100% load. The problem was the DisplayLink driver I use to display programs on a third monitor through a USB port.
Uninstalling the drive was not straight-forward, however, since it would not uninstall. Searching the Internet, I found the solution at DisplayLink's Web site: there are two parts to the driver, and the right one has to be uninstalled. Uninstall the product-specific software (in my case, the HP USB Driver for DisplayLink), and then core DisplayLink driver also uninstalls automatically.
(I noticed that DisplayLink has a 7-specific driver, which I downloaded but have not yet installed.)
Can't Write to File or Folder
Eudora email repeatedly displayed a dialog box, complaining it could not write to a file or folder, which might be locked or missing. Searching Google did not provide an answer, perhaps because Eudora is abandoned software.
After some mulling about, I finally wondered if a security setting might be in the way. Sure enough: for some reason, 7 prevented Eudora writing to its own files and folders. Here is how to solve the problem:
1. With Windows Explorer, go to the folder in which the program stores its data. For Eudora, this is C:\Program Files (x86)\Qualcomm\Eudora Mail 7
2. Right-click the folder name, and then choose Properties.
3. Click the Security tab.
4. Click the Edit button.
5. Under Group or User Names, choose CREATOR/OWNER.
6. In the Permissions section, notice that all permissions are turned off. Click the first one under Allow, and then notice that all others are also set to Allow.
7. Click OK, and then wait for 7 to changes the permission settings on all folders and files.
The problem is solved.
USB Drives Stop Working
After 7 is installed, the USB drives appear to work, but then stop in stages. First, 7 complains cannot find files being copied. Then it shows connected drives having no files of folders. Finally, Explorer shows no connected USB drives.
(By USB drives, I mean USB thumbdrives; other USB devices continue to work, such as the USB transmitter for my wireless keyboard and mouse.)
I found the problem and solution discussed on an HP forum: USB with External Mass Storage Not Working With Windows 7 x64
The solution is to install updated nVidia drivers from NVIDIA DRIVERS 15.49 WHQL. It'll require a reboot or two, but then the USB drives work again -- for a half day, after which the problem comes back. I have a call into HP tech support, so we'll see what they say. In the meantime, I note there is a similar problem with the iPhone and a certain type of Intel CPU.