I own TOPO! and it is a bitmap based software (the delorme is vector based) and is no where near as flexible as the Delorme. with TOPO! you can only zoom down as far as the bitmap goes, then it tells you, that you need another product to get lower. if you want it, i will give it to you for free. i HATED it, and once mobycat showed me the Delorme, i was in heaven.
Topo! was great for marking waypoints and trips, the garmin software is great for the management of garmin GPS units, but the delorme was just really great all around. there was one other i tried as well, but i forget which one now.