It would depend how genuinely useful it is.
I have passed up on SO many automated ways of getting iTunes Artwork because:
1. They tend to be slow
2. A lot of the time it's automated, and you can end up with the wrong artwork
3. I find I can get a 95% success rate myself and i can do it quite fast- maybe 3-4 albums a minute.
Do remember that most people will only need to run an automated app like this once or twice, as from then on you can just get the artwork off the internet for every few albums.
To be really useful it will have to be more simple and more integrated than:
1. Click on album
2. Open safari - go to amazon
3. Seach for album/find it click on artwork (usually a 2 click preocess)
4. Drag artwork to the window in itunes.
And if there was something that did this task REALLY well, I'd pay maybe $5 - but that's cos 95% of my stuff already has artwork and the other 5% I can't find (obscure non-retail discs and stuff). For people with 0% it will be worth more, but as i say, if it's automated, it'll only be run once or twice.
Good luck!