XMS 3 is the budget flavour of Corsair RAM. Its never the fastest nor is the most overclockable, in fact its stock!
But thats why your buying it surely, if you want more then view the range and see that there is more.
As far as normal RAM goes its great. Great becuase this RAM has proven so much more compatible than alternative products, I have had more success when building systems with this stuff than any other type of memory. I find that most boards I throw this RAM at accept it well with not tweaks needed. Older systems seem to accept it also, and it down clock too. My old system ran this RAM at 1333 and I had some 1333 stuff running at 1033.
All in all given the price point I like this RAM its my favourite for system building average PC's.
Heat spreaders are solid, not flimsy and I will bet they are not for fancy either, the modules after use come out of systems feeling no warmer than lukewarm.
I've got this memory since I've had my pc. I'm running it together with 4 giga bytes of kingston RAM.
My first 4 gigabytes were corrupt and I had memory errors. It was a really strange case and it couldn't always be detected by mem test. Sometimes it did, and I made photo's of this when I RMA'ed it. After 6 weeks (a bit long in my eyes...), I got 4 GB of new ram. So it took a while, but they didn't complain about the fact of not being able to see the corruption themselves.
After that if worked like a charm, and still does. It is pretty fast compared to my old memory, but that's of course also because that memory wasn't 1600 MHz.
I would definately recommend this memory to my friends as I already have done so twice, and fortunately they have both never had the issues I had.