I bought this yesterday, it arrived today, it took five seconds to install and I'm using it right now.
I was really expecting more from it. I had 3GB or RAM in my system and bought this to replace my 1GB card, thus maxing out my system at 4 GB.
If I right-click "Computer", then go into "Properties" it says 4 GB, but when I "Ctrl + Alt + Delete", "Task Manager" and then "Performance", it says I only have "3072 MB" (3 GB) of physical memory. I knew that because I'm running a 32-bit version of Vista it wouldn't show the whole 4 GB, but I'd read on several websites that it'd show up as 3.5 GB, which is what I was hoping for until I can get a 64-bit version of Windows Vista Ultimate.
It's not a bad product for £13, but really for people with 1 GB or less, or someone with a 64-bit version of Vista.
Since originally posting this comment, I have dual-booted my PC with Windows 7 Beta 64-bit, and it still doesn't read the whole 4 GB. This is more likely the OS than the RAM because when installed along side a 1 GB card, it shows a whole 3 GB (just like with my original installed 2 GB card).
I got some stick for only giving the card three stars. I gave it three stars because of my neutrality on the product, but I'm willing to put it up to four because I'm a little happier with it now than I was.