Goddamnit, I just typed an enormous reply and my browser crashed. OH well, I'll try to sum up:
I heard for years and years that Milwaukee Metalfest was a horrible thing, and to never attend - but I decided to take a chance last year when the line-up was incredible (Katatonia/Anathema/Opeth). While I've been to Roskilde fest in Denmark, which is an enormous open-air week-long fest, which Milwaukee can't compete with - MMF is good for what they are trying to do. I had a good experience at MMF. That's what it's about - sure the acoustics aren't too good there, but it is a lot more than just seeing bands. There are thousands of metalheads, some with similar music tastes to you that you'll meet, and tons of vendors selling stuff that might be hard for you to find. I went to a pub the night before Milwaukee began and happened to literally run into Mike/Peter of Opeth and Jonas/Anders of Katatonia outside. Anathema was inside and actually played in front of like 100 people that night. Experiences like that are fucking incredible...
The festival itself had its ups and downs, but hanging out/drinking with Anathema and seeing all three bands perform within a 2 day period was great. I can't speak for other years of the fest, or other fests that Jack organizes, but at least last years fest resulted in some really great memories for me. Having Endtime dedicated to me by Katatonia didn't hurt either

. I think Anathema had the best soundman working for them tho.. amazing performance..
PS: Katatonia wasn't pretty bad.. not perfect, but I didn't think Opeth were perfect either (sacrilege!). The EXPERIENCE of seeing both that night was surely incredible however.