over here in the US, we have these outdoor amphitheaters that are around 6,000-12,000 estimated size places. They are generally seated areas with a nice sized lawn area in the back.
That is the type of arena most of the gigantour gigs are being played in. I have no idea how well the tickets are selling in most of these places but I do know that Dave did a pretty good job at selecting bands.
You will have the megadeth fans of course. Dream theater and Symphony X fans are usually similar. There is a nice sized Nevermore fan base. Anthrax hasn't played up there in Western Canada and the Northwest US in a bit especially with this lineup. Alot of people in the US aren't willing to travel around for gigs like the metal fans do in Europe so I know for a fact that alot of people in these areas haven't seen Anthrax yet this year with the classic lineup.
You can see the interest for this tour over at
http://forums.gigantour.com
I won't know for sure until later this month but the stars seem to have aligned well for me. I really can't take anymore days off for most of the rest of the year so I like how the Portland and Seattle dates are set up plus they are conventiently not too far from airport/hotels.