I've used DaisyDisk occasionally throughtout its history from 1.3 onward. After all, this isn't a program you use daily, just that once a quarter or semi-annual cleaning you might need to do.

It's been stable on every launch, and does precisely what it advertises. It scans the drive and locates the largest usages of your disk space in a very intuitive circular map which will quickly let you visually drill down to where you may have items you had forgotten or no longer need. Sure, you could do this by scripting from the terminal, but that wouldn't be nearly as easy to use, plus you can't show it to your SO and say: This is why we manage files.... Note that the scan is a bit slow, but I've got a 320GB 5400 rpm laptop drive with 100s of thousands of files on it, so that's to be expected. It's a lot of data.

A couple of nice additions would be the following:
* Store the last scan for "historical" purposes, or in case I did something silly like close it before I was ready. (by preference, of course) This could also be shown while a new scan is in progress. You should also be able to select a folder to scan directly out of such a stored map.
* The ability to have multiple HD scans ready and selectable would be an easy add if the last map of each is stored.
* The ability to select pieces for deletion
* The ability to delete those, either to the Trash Can or delete permanently.
* The ability to find duplicates, since we have all that information in memory already, name and/or size matching should be a cinch and could go on behind the scenes. Again, this is not an app you run continuously, so if it actively does background processing while you're looking through your disk map, that should not affect anything.
* The ability to delete dupes under a target tree.

As for value, well, I got mine as part of a bundle, so the value was very high, as it was a pleasant bonus in that particular bundle.