I took a trip from Mill Ave in Tempe to downtown Phoenix to watch an event.
Pros:
Cheap Tickets
Smooth Ride
Cons:
1) Doesn't cover the whole metro area
2) Anyone can just hop on here and get a free ride without checking ticket.
3) People getting harassed by homeless drunks. (see #2)
I've taken many heavy-rail / light-rail trips in New York via Metro North and in the San Francisco Bay Area (BART). This one kind of sucks.