Scenic Map does not yet take advantage of the iPhone 4's Retina display resolution but it still looks great. Scenic Map has software anti-aliasing which eliminates jagged edges and makes the original iPhone display look almost as good as the iPhone 4's Retina display.
Scenic Map on the original iPhone display
Scenic Map on the iPhone 4 Retina Display
I highly recommend upgrading to iOS 4 on all your iGear when it becomes available (the iPad version will be released later this year). The biggest improvement you will notice when using Scenic Map is that the pinch zoom has been fixed. In iPhone OS 3.x the pinch gesture zooms half as far as it should. This makes the pinch zoom feel sluggish. In iOS 4 pinch zoom feels snappy and precise. In future versions of Scenic Map I plan to support the multitasking features of iOS 4 which will allow continuous tracking when the app is in the background.