Everyone here has some good insight on what the con is like, but nothing replaces checking out the convention for yourself.
Both the Alexis Park and Cashman Center locations are flawed. The Cashman Center is far from close by hotels and it isn't the safest area to be around at night. Alexis Park is too cramped and claustrophobic since everyone was dying to be indoors to stay away from the intense desert heat. I was at CES earlier this year and I checked out the Renaissance hotel where Anime Vegas 2008 was held and I thought it would be a better location for future AV's; safe area, close to the monorail, nice hotel, etc.
I've always liked the guest of honor line up. You get some pretty awesome American voice actors with the occasional Japanese guest.
Personally, I wouldn't mind if Anime Vegas changed the date to sometime in the fall, like kinda close to Halloween-ish.