I use my TomTom all the time - but still keep a good map nearby to do a general area check of major routes, towns, etc prior to setting out on any trip to avoid treking off too far in the wrong direction.
Flew back yesterday from a week of Sonapicino winery visits* - left SFO on a 757 which - from the visible landmarks - angled SE across CA from SFO to cross the Sierras near Yosemite and pick up I-40 near CA-AZ border - E along I-40 to Amarillo and then US-287 SE past Wichita Falls into DFW. GPS works fine but following the ol' NORM (Nap Of Road Map) is never entirely out of date.
Richard's $.02
* Usually no more than 3 per day but set a new personal best on Sunday with 8 in the Russian River Valley.