I can see that a number of people have successfully recovered failed disks, which is great. My experience was the opposite. A firewire disk was in standby, we had a 10 min power outage, and the directory information became inaccessible, OS X would no longer mount the disk. I checked the reviews, and based on the product information and reviews, thought DiskWarrior was a good choice to recover the data. Since the disk was not in use at the time it seemed reasonable that the files were still there.

Well, DiskWarrior said the disk partition was impossible to recover and thanks very much for the $99. (Actually, it didn't say that last bit but you get the idea). It suggested Alsoft technical support might be able to help further, which they didn't. Before they got back to me with their polite but fundamentally unhelpful emails, I had downloaded the demo of DataRescue II, seen that all the directory information was intact, and recovered the entire disk (110GB of EyeTV recordings) after buying a license.

Alsoft had nothing to say about the fact that DataRescue recovered every part of the data - files, folder, directory structure - without breaking a sweat, while their product insisted the data was unrecoverable. I think before even trying this product you might want to grab the DataRescue demo - at least you can get some idea of whether the data will be recoverable before you shell out what is a large amount of money for a piece of software you may not use often.