I've been 3 times, and will be going for my 4th this year. I have never gone on the tactical. My first 3 times going have been for unit "reunions" for retired and current members. This year, I'm falling in with a different unit that uses it solely as a training event. I have lately enjoyed the Axis cafe, and my British unit will be wearing our alternate Axis uniforms to attend this year. That is a nice recent attempt to improve the experience for attendees. The flea market is also still a pretty good place to find things you can't find elsewhere - although I'm going to cry when I pass Lost Battalion's old building and they're not there.
I think it's a mistake to see the Gap as a reenactment. I tend to look at the Gap as being like a national WW2 reenactor convention. As with any professional convention, very little real "work" gets done there. Instead, it's a place to network, do some shopping, have a few drinks with old friends, and for sub-organizations to have a central forum to meet and take care of business that can't take place in cyberspace or over the phone. If you think the Gap is expensive, believe me, you don't want to know what it costs to attend other conventions (entrance, hotel, food, entertainment, etc.).