I have a Garmin 60CSx and I love it. When I bought it, it was one of the most highly recommended units on geocaching.com. I haven't had any complaints or problems with it in the time I've been using it.
I've heard mixed reviews about relying on the iPhone for geocaching. Most people I know use the geocaching app for information about the caches they are looking for, but use a separate GPS for the actual coordinates. I don't know if it's because the iPhone's coordinates aren't as exact or if there's some other reason. The iPod Touch won't work at all for geocaching, unfortunately.
I agree with jme829 that your best bet is probably to read the reviews and suggestions on geocaching.com to find what most people are recommending lately. Also, if you are looking for other gift ideas and your husband isn't already a member, you should consider getting a membership to geocaching.com. It opens up all sorts of addition features, and there are many caches that are available to members only.