I'm quite new to geocaching as well but I'd say the map requirements all depend on the type of caching you'll do and whether you will use the gps for anything else like hunting, etc. Almost 100% of the time I use the compass function as the primary guide once I feel I'm nearby or on the main trail to a cache. But I agree with the first two posts that maps are quite useful - and more fun at times too. Last night during a night caching excursion (not using coordinates to find the cache) it was pretty helpful when we thought we had been everywhere to pull up a satellite image of the park (with our "tracks" displayed over most of the trails) and know there were a couple trails we missed.
My favorite part about geocaching is that it brings you to explore places you've never been. Most of the caches I've done were near good trails so I wouldn't say a map is entirely necessary. Though if you plan to go bushwacking and incur difficult terrain or longer hikes I would recommend a GPS with topographical/arial mapping capabilities. Seeing where you are relative to a road, lake, ridge or valley is as priceless as it is comforting when you're deeper in the wilderness.
