I use iGO...
And here is my beef.
Coming from iGuidance v3.
I really like iGuidance v3 but I'm finding I like iGO better. iGO is very graphical and mostly eye candy. I was always a 2D buff until I found iGO. Motion is very fluid and you can use the D-Pad to rotate the map and zoom in and out.
Also there is a View button which is very handy. Tapping it cycles through 3 views. One is standard first person view, second is ???, and third is a completely zoomed out 2D which just shows the entire route, which is nice because you can get your sense of direction down.
Another thing I noticed is that it isn't sold with US maps, but will work if you have compatible maps. And to change states to find a destination, you have to click "Change Country" button. (In EUROPE, states = countries, kinda)
Another thing is that iGO will remember your route and current location on power off. So if your battery dies or you just decide to turn off your Axim while your driving long distances... you can power on the unit and your current route will be saved and your last GPS position (which gets updated once your GPS gets a signal.)
You can also minimize iGO to the System Tray.
Other then those differences it works much like iGuidance.
Some reasons to stick with iGuidance would be that I think that the voice guided directions are a bit more helpful ("Drive 100 miles").
Also iGuidance has local routes (backroads). The wierd thing is that iGO has a checkmark allowing/disallowing highways. Unchecking Highways (should be local) will turn up completely different paths then iGuidance's local routes. This sucks because I have to drive through downtown regularly and avoiding the highways downtown is faster. iGO had me going crazy routes that strayed from the best path.
I think iGuidance has better local (no highway) navigation.
Also I like iGuidance because it would tell you when to exit, where iGO tells you to "Merge Right"... but driving on the highway for miles, you normally hear "Merge Left"... "Merge Left"... "Merge Left"... "Merge Right"... "When Possible make a U-Turn"
Basically iGO has too much added vocals that aren't needed. Just tell me to "Keep on highway for next 50 miles"... then shut up until I'm 5 miles away from my exit.
I've noticed that iGO doesn't say exit numbers like iGuidance. iGO tells you the name of the exit... but that isn't helpful when you don't know where you are. If you need to take exit 10... and your at exit 5... that lets the driver know that you are 5 exits away.
All in all I really like iGuidance. I also really like iGo. iGo is really fancy and it does the job. I always keep a copy of iGuidance for backup because I know I can trust iGuidance.
Conclusion? Well I haven't launched iGuidance since I installed iGo. iGo's maps are state wide can can be launched just by copying the files into the maps directory. This is nice because you don't have to "Create a map" like iGuidance. I keep the US maps stored on my 8gb CF card and just copy over the maps I use the most.
Pictures here