When I was in the Phoenix area last year, I took all three loops (starting with the partially constructed 303 that morning) and just plain gawked at the stacks. I especially appreciated the stack when I went under it on I-17. The short stack is nice too - but compare nothing to the SuperSanTan - red and all! I was last in Phoenix as a kid in 1983(ish) and back then the Superstition freeway ended at Gilbert Road and was 2 or 3 lane nearly all the way - the short stack didn't exist and the Stack was not all there. Now with 5-6 lane Superstition, all those loops and stacks - I just was plain amazed by the architecture.
Phoenix grows out - not up, and the freeways accommodate for it. They can build them that wide there unlike NYC, Chicago, Philly SureKill, Pittsburgh, etc. Interchanges can be large enough to prevent traffic from slowing down as it transitions from road to road (just like Texas). The freeways grew as the metro area grew so (IMO) the chance of NIMBYism was less (Though it does exist)