Aspire series is intended towards the home / small office and will have the widest range of available options and price points. TravelMate is Acer's "business" line. Generally the "business" models from a notebook manufacturer hold up better than their "home" counterparts. However, many times there was little or no difference in the actual machines (Dell Inspiron 2200 versus Latitude 110L or Compaq EVO N160 vs Compaq Presario 1720). Again, though, sticking with the business line is never a bad idea, even if they are a bit more expensive (plus might get different support numbers and other expidited things)
My experience with Acer Aspire series is the chassis semed to be a bit flimsy and the Western Digital Scorpio hard drives they used were. . . wonky from time to time. I never became a fan of the curved keboard.
Where we used Acer we always dealt with a local rep so I can't speak to their end user support.
I've had very good experiences with AOpen as an end user, though.