Just found the current issue of Grooves, with Autechre on the cover.
My current favourite is
Outburn -- lots of alterna and darker side stuff. Reviews are excellent. The first sentence is actually an attempt at describing the music, so that you can decide whether or not you want to read the rest of the review. I'm subscribing to this one.
I will also second Wire and Grooves. I also just found something called EI (Music Electronic and Otherwise) (spinoff of the defunct I/E?). Haven't read it yet.
EDIT: Okay started to read it. The reviews are pretentious as L (think review by analogy to clouds, nature, and nanites), but make for enjoyable reading (I listen to prog after all, so a certain suspension of criticism is in the blood). High marks for attempting to be honest. Appears to be a one-guy operation.
Here be the URL:
http://www.ei-mag.com/
Also, for progressive music fans, Progression.
Also, for current alternative music (which includes a bit too much nu-metal and emo for my tastes, but...whatever), AP -- Alternative Press. Pretty good reviews, but they vary. Kind of like Spin is to Rolling Stone, I.E. sometimes better, sometimes worse.