im a new cacher.. Tugies got me into it while she was on my tour bus afew months ago. but since then ive paid for the app on my Droid phones, and also a permium membership.
no need to buy a GPS if you have a decent smart phone and plan only to do caches in phone signaled areas.
i have almost 40 caches to my name at this stage all done with my phone. ive found no real problem doing it this way. but when im out of phone signal like i often am for work ( out back tour guide) i cant cache.. im yet to work out how to down load pocket quereies to my droid device and save as offline points.
so you can cache comfortably in metro areas that your phone carrier has coverage. a dedicated GPS will be handy for the further out ones out of phone coverage.