As above really. Am getting a 3GS to replace my 1st Gen iPhone and would really like to use it as a trail finding GPS.

I've been using the Lite version for a while now. I liked it so much I went for the paid version.
Doesn't do anything fancy but it works well and is easy to use.

D'you know, I downloaded it a while back, and I haven't used it yet… 😳

Sounds good… I wonder how well it will work in my CamelBak pouch.

Also… one concern is the battery life. A little concerning if I am in the back of beyond trailfinding and it drains the battery to the point where I can't call for help when I pin myself against some gnarly rock.

It does work, even from a backpack. Downsides, it needs a phone signal to download the maps as you go and yes it does eat battery life, 2 -3 hours from fully charged to flat. Also you really don't want your iPhone on your bars, they don't like water and are fairly fragile so you're back to stopping and taking your pack off to navigate.

Bum… thought so.

I guess a Morphie Juice pack and a solar charger could be the answer?

Or one of these and a long lead to my camelbak strap

thought id post this anyways , im sure you all know the tips for saving bty life.
http://www.apple.com/batteries/iphone.html

I think the battery problem is compounded when we (mtn bikers) use the phone as a GPS because we are usually miles away from normal civilisation and the farther you get from the cell the more power the phone uses to keep signal strength.

It would be much better if the map was onboard rather than relying on Google via data from the cell.