I've been using Gaia GPS on the iphone - it's also available on android - It's not too bad. My only problem with the iphone is battery life.

the main thing I've been using my phone for on hikes has not been that - it's been reading - using the amazon kindle app. the phone is lighter than a paperback - and the battery lasts a good long while in airplane mode. Trouble is I do have to take it out of airplane mode to use it as a gps, and then I may find I'm not reading to instead use the phone for gps.. so the jury is still out on whether I use the phone, or get a separate gps.