I am looking to buy a Garmin Dakota 20...should I purchase the package with theGarmin MapSource Topo U.S. 100K DVD? Or should I be looking at other maps to purchase? I am mainly planning to use for hiking and geocaching. Thanks for all iput!
Garmin 20 is a great unit. I wouldn't spend any money on the 1:100 000 maps. You'll find more useful maps for free here.
It depends. IF you find a really good "bundle" deal, there's no reason not to go with it. I also like the maps available here (and made some of them myself), but there are still a few advantages to Garmin's product.
With Garmin, you get the whole US, ready to go without downloading and installing separate maps. They are also seamless between states - you may have some issues combining different maps from here in there areas where they meet/overlap. Garmin's maps have DEM data that produce shaded terrain and 3d views in Basecamp. This can be useful in determining track profiles, etc.
But if cost is a factor, I'd try the maps here first and you could always purchase the DVD later. Note that you won't be able to install the entire US from the DVD due to technical limits on the GPS. If you want to have the whole US topo 100k available on your GPS, you should purchase the version on a pre-loaded memory card instead of DVD.