Yes, it's a good one. Nice form of delivery too - a bootable CD that automatically kicks the test off.
It does the same tests as Memtest.
Keep in mind all software based hardware diagnostics suffer from the same problem: You are trying to get software to run properly on suspect hardware. It's not unlike walking into a loony bin, handing a clipboard to some nut and telling him, "Ok, go ask everyone here if they are sane or not and record the answer for me."
You can get false negatives (everything is fine) but typically won't get false positives (meaning things are broken). Positives (errors) don't always mean what they say but it's a good starting point. "Bad memory" can be the memory itself, bus, controller or even CPU/PSU.
