I saw Tool last month in Milwaukee with Tomahawk.
I must say that Tomahawk was ABSOLUTELY THE WORST EXCUSE FOR MUSIC I have ever seen. We thought they were maybe doing a joke and sounding horrible for a while and would then start jamming and be decent. Everybody was yelling at the band, flipping them off, throwing crap onstage, etc until they finally left.
(Think of Tomahawk as a group of high school kids playing in their talent show; only these kids are totally deaf and cannot even hear what they're playing)
I would recommend skipping Tomahawk if they're still touring with Tool because of how much they suck; however, because they suck so much it's almost worth seeing for a good laugh.
Tool Rocked - sound was great, screen show was great, song list was awesome - couldn't have been better. That's all that needs to be said.
Note that they did perform one song with 2 dudes from Tomahawk who did not suck during that part, but they weren't playing their "music" anymore, so that doesn't count.
Definitely worth seeing.