I don't have much faith in using SMART status to monitor a drive. If you experience a single head crash, many of those utilities will start providing what looks like an "imminent doom" status, even though the drive may still be correctable and work for years. I don't believe SMART monitoring actually reports where the failures on a surface scan are, just that they exist.
For me, nothing beats a real surface scan. I think the two best tools on the market for that are TechTool Pro and Scannerz.
TechTool Pro:
http://www.micromat.com/techtoolpro
Scannerz:
http://www.scsc-online.com/Scannerz.html
Each of these has its plusses and minuses. TechTool Pro has SMART monitoring in the program, and it can perform a somewhat crude surface scan. It also has a lot of other features.
Scannerz does drive and system testing only. I think it does a more thorough job of scanning and that's really all it does, but then again it's a lot cheaper.
The nice thing about either of these is that they can both tell you where the drive problems are. If a drive has bad sectors in a limited region, the drive can be reformatted and the bad sectors reallocated to spares. I've seen drives like this last for years, but SMART tests continue to report "imminent doom." If the drive has severe damage, so much that it will eat up all the spare sectors and still not be fixed, you can often partition out the bad region of the drive and put the drive right back into use. I know of one guy that did this on a drive on an iBook G4 w/100G drive and he's been using it like this without problems for about 4 years.
I think the trick to do this on a single volume drive is to create a volume that ends before the damage begins, create a volume that starts and ends right before and after the damaged region, and then a final partition for the rest of the drive. After you do this, highlight and delete the volume containing the bad sectors. You end up with a two volume drive, but hey, it's usable!