iGuidance (3.0) is software available directly from NavTec, the company which makes most OEM mapping software, as well as google's maps! The only experience I'd had prior (besides google) is with an OEM Volvo system which is, quite simply, crap. I'm very happy to say that iGuidance, in conjunction w/ my carputer's touchscreen is far better.
It has far better coverage then does Volvo's, although I'm not sure its quite as good as google's.
Searching for POI's is better then with google, especially when looking for parks (national, state, county, etc). While Google is improving, you basically have to get it perfect or you might get suggestions, or nothing at all (especially with parks with multiple names) However on iguidance its trivial
Entering in addresses is also quite painless, despite the low specs in my carputer mini-itx board drawing ~9w) it rarely stutters
Reroute time is also quite fast, on the order of 1-5 seconds, depending on length of reroute, the initial calculation only takes about 5 seconds as well, even if your going 500+ miles, far faster then any OEM system I've used, and faster then some other programs as well (like DeLorme)
Finally, its very touchscreen friendly, although I find UMPC mode to low of a resolution (I do have an 8" monitor though)
However, while the detour botton seems like a great idea, I've found it relatively unpredictable and useless, I have more success just getting off the road and hoping it will (and can) reroute me.
Another gripe I have, which may be isolated, is it will not let me take page mill rd (los altos, ca) to get up to skyline, it continously tells me to do a u-turn, then after about 20 mins, shuts off. This is the only road I've found like this in the year I've been using it.
Improvements I'd like to see is multiple route options, where either it calculates 3 routes and I choose (based on experience or its estimated times, like pioneer's) or i can cycle through routes.