-- Last Updated: Jan-29-13 3:57 PM EST --
Machias has a reputation as a challenging river. It does have a day or two of lakes at the start, which of course can be skipped. I was going to do it late last May. The water level was marginal. We started but I bailed out after two days when my bowman got sick, and that was before the most challenging sections.
Plan on running your own shuttle. There is only one outfitter that shuttles on that river and their prices are, IMO, exorbitant.
The St. John can be fun but you might be disappointed in the rapids, class II - III. Still worth it, IMO, because of the remoteness. It's a long way between humans. You also have to give a wad of money to the Northwoods, which you don't on the Machias. And the shuttle is longer, but cheaper. You finish up the same as the Alligash, which sounds like you might be familiar.