India Pale Ales (IPAs) are an acquired taste. They have a very strong flavor profile due to the concentration of hops utilized in the brewing process, which gives it a strong bitterness and fragrant aroma. I have grown particularily fond of these beers because I enjoy the real distinction of the smell, taste and feel of the beer. My lovely wife strongly disagrees with me and gets bitter beer face each time she takes a sip.
Hops are the primary driver of the flavor, aroma and bitterness of an IPA. The term IBU (International Bittering Unit) is based on the amount of hops you utilize to get a beer more bitter (malt will often offset the bitter flavor, so malty beers with a higher IBU may not be all that bitter). The higher the number, the more bitter the beer typically. Most IPAs run about 60 IBUs. To put it in perspective, I would say that most other beers run 20-35 IBUs. Double/Imperial IPAs will range in the 90+ IBU range. I've had one that is 120 IBUs...wow!
Lots of flowery, sometimes citrus-y scents due to the hops. The flavor will be somewhat different depending on what hops are utilized in the beer. Expect bitterness and don't complain if you have an IPA and don't like bitterness. Color will run from a light amber to a dark copper. The alcohol content on these beers run on the higher end, typically 6%+.
Past reviews of IPAs have included Flying Dog Snake Dog IPA, Marble Brewing IPA, Dogfish Head 90 Minute IPA, Stone Cali-Belgique IPA, Four Peaks HopKnot IPA, Four Peaks RAJ IPA, Hales' Mongoose IPA, Alaskan Brewing IPA, Redhook Long Hammer IPA, Green Flash Imperial IPA, Marble Brewing Double IPA, Carver Cascade Canyon Cask IPA (say that three times fast), and the 21st Amendment Double Trouble Imperial IPA.
In terms of other IPAs to try out or that you may see around town, there's Chama River Brewing's Dr. Strange Hop, Turtle Mountain Brewing IPA, Stone IPA, Boulder Beer Mojo IPA and Il Vicino Wet Mountain IPA and the Prescott Brewing Ponderosa IPA.
You'll find that almost any brewery will do an IPA - some get really into them, but I haven't gone to a brewery yet that didn't have at least one on tap.