This was my first trip to Historicon, and only my 5th convention total (the others being twice to MilleniumCon in Austin, one each to TwinCon in Minneapolis and GenCon in Indianapolis).
I enjoyed the games I played, and I think it was pretty well run (although pre-registration and other on-line support was not as complete and user-friendly as GenCon). The dealer area was great, and the cost ($10 for a whole weekend of gaming!) can't be beat.
I was not overwhelmed by the environment. The Lancaster Host seems okay (I did not stay there)but was MUCH too crowded and poorly layed-out for a convention. I think Historicon would be a better convention in a larger, more modern facility, even if it meant charging more for registration.
Finally, I think Historicon could benefit from having a few seminars (painting, figure modification, terrain making) similar to GenCon, and perhaps some lectures/workshops whatever on military history, tactics, rules design, etc.
All in all I would give it a B+, and will probably go again, but perhaps not as early as next year.