I got speeds between 40 MB/s and 55 MB/s while copying a few 1GB files to this USB drive from a WD Caviar Black 1TB in Windows 7/64 bits.
There was a problem at first. I already had a drive of the exact same model working fine with this PC. The new drive refused to show up in Windows Explorer. The Disk Management applet in Control Panel showed it, with an icon near it and this tooltip: "This disk is offline because it has a signature collision with another disk".
It turns out that both USB drives came from the factory with the same signature and Windows 7 can't handle this. Microsoft was wrong to make this a fatal error. WD was wrong to miss this in testing - they were supposed to know about it and assign a random number to each drive to work around it. What, they never expected a customer to buy 2 identical drives?
Here's what I did to fix it:
Click the Windows start menu, type cmd, right click the "cmd.exe" item that appears at the top of your menu, click the line "Run as administrator"
Type these commands:
Let's say your new drive shows up as "Offline Disk 5". Type these commands:
select disk 5
Let's say you got a bunch of hex digits like 0004536A4 or whatever. Type this:
uniqueid disk ID=0004536A5
That is, change the existing id to something slightly different so it doesn't conflict with the id of your other drive any more.
Close the DOS prompt, disconnect the USB drive and reconnect it again.
If it wasn't for this behavior, I'd give it 5 stars. My other drive (same model) has been working well for months after all. It doesn't get hot, it doesn't make noise.
Update (Sep 2012).
This time I bought a WD 3TB drive. (For some reason Amazon's site is unable to distinguish between the 2TB model and the 3TB model and it puts all the reviews together, making a mess.)
I was a bit worried about the 3TB part, because my ancient computer runs XP 32 bit (SP3) and I knew there was a limit at 2 TB. Well, somehow the thing worked. I plugged it in, did NOT install any drivers or any software, it just worked. It showed 2.72 TB free (which is about 3,000,000,000,000 bytes and allows WD to shamelessly claim 3 TB, LOL). I could copy about 12 GB to the external drive and read it back without any problems.