OK lets get a few things stright... ... The Alcoa wheels are Forged, they have a much higher weight rating and they have a very much better finish. There are several Non-forged wheels out, American Racing, Eagle a new wheel company called Ion Alloy, and Mickey Thompson. The cast wheels are much cheaper, and like anything now-days you get what you payed for. Cast wheels are more prone to crack when damaged (like hitting a curve, large pot hole,ect) where forged wheels will bend, they also can be repaired. The finish on a Cast wheel isn't as nice and will not hold-up to the elements like a forged wheel.
SALT, yes salt is bad for aluminum wheels, it's bad for anything it touches. It will make wheel maintenance a little more active, but that is just the nature of the beast. Alcoa is the number one producer of aluminum wheels, in the world. They do make 16" dually wheels and singles for our trucks, but granted this is just a very small fraction of the industrial involvement they are in. They manufacture the number one aluminum wheel for tractor trailers, which most everyone has seen shining on those big rigs. But they are the number one maker of aluminum wheels for many, many other areas such as large commercial aircraft and even the space shuttle. They are #1, because they make a very good wheel, not just a pretty one. The over the road rigs drive in all types of weather, and they still maintain a nice look. Most people including myself will use a sealer to help keep the wheels looking good. Aluminum will oxidize when exposed to air, and corrode when exposed to salts. These sealants are available to help keep that shine by keeping out the unwanted.
I got my wheels from Southwest Wheel, they were not only the cheapest, but the most knowledgeable. They new their product, and keep me informed, I would recommend them to anyone considering a Alcoa wheel purchase. Southwest Wheel also had new steel dually wheels, for the inter wheel on the back of a dually. I found this perfect, and it allowed me to have two complete sets of tire/wheels for my truck. The price of the steel wheels were only slightly more then what the local junkyard wanted for used ones, and I don't have to worry about bent, out of round, or leaking wheels.
What ever you decide to do, do not go with any Aluminum wheel that has a clear coat applied to it's finish. Although it sounds like a good ideal, no matter what the salesman tells you it will yellow, and peal. Once that happens you have to get all the clear off before you can re-finish the wheel.
My wheels are "Summer" only wheels, but any Aluminum wheel should be sealed, this not only helps with salt and oxidation, but also brake dust, water spots and dog urine!!. I bought my supply of Zott seal from a hot rod shop called RBS online, but it is offered at other car parts stores. I will be applying the zopp seal to my ALCOA'S in the coming weeks, I'll let you no how it went. This stuff has been around for a while, alot of professional racers, and show car guy's use it to keep there shinny aluminum parts shinny.
Also when ordering your wheels, don't forget or cheap out and not get the caps, lugs, and covers. They are very nice looking and set the wheels off and complete the installation. When you order you can also take advantage of getting the later model wheels which have about 3/8" more offset, this will help if running over sized tires.
Attention: TDR Forum Junkies 
When I do a tire rotation it runs around $60. 
