I personally find the maps much better too (it even has house numbers if you need it) the directions show at the top of the screen (like a car Sat Nav) and if you loose the GPS signal you dont get stranded.

I used Google maps previously and got seriously lost in the depths of Somerset when I lost GPS signal but Skobbler still works offline that for me is the biggest advantage.
I think you may be confusing online and offline with GPS signal a bit. These Apps work with either or both an online data connection via the phone itself or a GPS signal via the GPS antenna. When they say they work "offline" or when you don't have a signal they mean it works using the GPS antenna only. Lots of the free ones don't work "offline" or without a signal because they require a data connection as well as a GPS connection (this is why they fail in more remote areas with poor phone signal). The worst issues I had with my phones GPS antenna was actually in built up areas where the half assed attempt at a GPS antenna couldn't get a signal.

I could be wrong and Skobbler could be different but I don't see how it could know your location without either a GPS signal or a data connection.

The iphone battery life is really poor though for me 2 to 3 hours with the Sat Nav and it's dead. I carry an Anker charger with me at the mo but am looking at hard wiring it.
12V fag lighter socket of fleabay, you can even get a little adaptor for it to take USB cables, around a fiver. I have mine fitted under my seat problem is though my battery is fairly small and my charging system seriously lame so Phones and GPS can kill it really quick. Great for charging my e-cig though.