I'm using Irfanview for its batch function. Many people don't know all its capacities. For instance, you can copy any set of IPTC metadata to any set of photos. Just hold the CTRL key down when you click on photos here and there. Under the options tab, you can even specify you want to fill up only empty field in the photos, or override with selected (non-empty) fields in the template.

What I would really like is a function that goes through all your IPTC metadata (of a selected set of photos) and does a search and replace. That's very much needed when you made a typo, for instance in the keywords. Anybody knows a program that can do that? More possibilities: extend keywords, e.g. replace "water," by "water,wet," all over a folder. It would be nice to have a wild-card option, or a confirm screen Y/N on every photo. Aaaah, and I'd like a statistics page, where all your keywords are listed, prefereably with a thumbs page where all the photos appear that have that keyword. Nice way to find improper tagging or typos.

I'm still looking for the mother of all tagging programs, preferably with a built-in spell check.