Welcome to WebmasterWorld Guest from 220.127.116.11
Only problem I've seen is between different version of perl and/or imagemagick. For some reason when I moved the same perl program to another machine the tagging jumped by about 10 pixel in relation to the image. Spent a long time trying to figure it out... and failed. I ended up just added code to change the positioning by 10 pixels. :)
A former coworker of mine uses ImageMagick in his photoblog business (mod_perl) and loves it. Think of having the basics of Photoshop (or Elements I should say) accessible via a webpage to get an idea.
If you would like snippets I am sure I could dig something up in this myriad of files I call a site, just let me know.
I can't comment on any php solutions since I'm still of the school that php isn't a solution. (Sorry, not a flame, just a small opinion).