Not for off-line use
It has an intuitive interface; easily integrates with Dropbox (and I guess iCloud and URLs as well).
But be aware that there is very little off-line capability. i.e. you can only open a new GPX file if you have on-line access; it seems that there is no ability to store GPX files on the iPhone. If you have a file loaded with no internet connectivity, then obviously the satellite imagery will not update, but since the GPS receiver should work, you should be able to determine whether or not you are following the pre-assigned path. However, until you get internet access again, this will be the only route you can see/follow.
Overall, I think its worth the asking price.
Norm212 about
GPX Reader