I have version 5.1 and have not experienced any problems or missing roads yet.... Denver, CO area.... I work on a Federal campus that is usually blocked out by some mapping programs - but the TCH has those interior roads. Also - they realigned a road in my area about 2.5 - 3 years ago and that realignment is on the 5.1 version which also impressed me....
I would venture to guess that they focus first on the major metro areas..... It's not an easy job to keep up with all of the roads, construction, and POI's over the entire US - that's a pretty major undertaking....
I just checked out Honda's site and it looks like their updates for 2006 Accords cost about $200....
https://iweb.alpine-usa.com/Hondadvdsales/naviorder.php
Maybe Toyota needs too looks at other sub-contractors for their data?
Here's an intersting article too:
http://radar.oreilly.com/archives/20...ata_pro_1.html