I have been updating motorways, bike paths and everything in between around Denver, CO. Among other things I have noticed and tried to correct:
TIGER street data: Topology and nodes seem to be generally correct. However, curved streets often appear as diagonal lines slicing through fields, houses, etc. Some streets change names upon crossing another, and the TIGER data often misses this. Away from Denver, there are many streets that are badly displaced or do not exist at all. I'm correcting these using the Yahoo photos and changing the tiger:review tag to aerial and then deleting that field as I bike or drive through those locales and verify the configurations.
HIGHWAYS: The differences between primary-secondary, secondary-tertiary and tertiary-residential designations might well be arguable. However, there are some obvious discrepencies between the map and ground truth that I'm working on. E.g., a portion of Deer Creek Road is designated as a primary route. Although bicyclists who fight traffic in this canyon might disagree, I believe it should be designated tertiary or secondary at best.
I have changed US-285 between N. Turkey Creek and Sheridan to a trunk route from a combination of primary/motorway as it is not completely limited access, but the major intersections do have grade separtions.
There are people-years worth of work left to do around here, so feel free to join the fun.