I have no idea how fast the "full" version runs. But the West regional version is slow as molasses. I was sold at the $25 price point, and had read favorable reviews. Now I don't know what the reviewers were thinking. It's practically worthless.
The big problem with the slowness is that you can paint yourself into a UI corner, and you're waiting, and waiting, and waiting to undo you mistake.
I also don't find the maps terribly intuitive: sometimes street names appear, sometimes they don't. I haven't figured out yet just when they do and don't. There's a setting for "street names" (why would you want to ever turn them off, anyway?) which was initially "off", but with it off it showed some street names anyway.
I've no idea how to turn on voice guidance. But I haven't tried it on a trip yet, either.
Honestly, I'm thinking that with a heads-up display, Google Maps would be a lot easier to use.
Are all GPS apps on the iPhone this slow? I'm afraid I'm now shopping for another GPS app.