If you've never seen a 737, A320, or CRJ before then you'd be in hog heaven.
Actually Sky Harbor has won numerous awards for terminal art. There are regular art exhibits throughout the airport, particularly in Terminal 4. The stained glass ceiling in Terminal 3 was recently restored, that might be worth checking out... from pics I seen it is pretty impressive. Otherwise there is your typical collection of fast food and sit down restaraunts to pic from in the terminal. Nothing like a non-fast food meal, a beer, and a seat by a window to kill time in an airport, IMHO.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia
IF you get the chance... take a taxi ride west on Sky Harbour Blvd to 24th Street...you can't get much closer to the end of BOTH runways, and the feeling of having those jets so close to touchdown as they fly over you is AWESOME!!!
When my grandparents were still alive (last time I was down was in 2000), I used to spend countless hours watching the planes until dark...and have many numerous amazing belly shots of planes as they fly over top of me... Sunburn notwithstanding...I LOVED IT!!!
I realize you will be there in the dark (damn that city gets dark quick!) but it's definitely an adrenaline rush... Just remember to carefully keep watch on your time... it's easy to get absorbed in the fun, but you could get an hour of spotting out there..and there is quite a few places for a bite within a few minutes walking time north on 24th. Also..make sure you have time to get back to the terminal! ENJOY!!