I've used Backcountry Navigator Pro and Backpacker GPS.
I prefer Backcountry and use it mostly to supplement navigating by physical map while backpacking. It has completely replaced my standalone GPS unit. You can cache topo maps along with aerial shots for certain areas, or download them on the fly if you have a data signal.
Backpacker GPS has the ability to download pre-defined trips, but it ended up being too complicated for the benefits. I used Backcountry Navigator Pro on a week-long Yosemite trip last year, and it worked great. The aerial shots supplement the topo maps very well.