A draft bill has been introduced (or is about to be introduced, I'm not sure which) in the Montana State Legislature that would ban the use of felt-sole wading boots while fishing Montana's waters. According to the current draft, the regulation would go into effect on October 1, 2012. Hopefully that gives you ample time to wear out your current felt boot and buy the next big thing. I'm not sure that it gives boot manufacturers ample time to come up with something equal to felt in the stickiness and safety departments, but maybe.
Overall, The Eddy supports the bill. There are a few idiosyncrasies that make me cock my head in confusion (you can check out a decent discussion of the draft bill over on The Headhunter), but I think in the end its a good idea. TU has been banging this drum for awhile because felt soles (along with many materials common to wading boots) are prime transportation for invasive species. So in the interest of fisheries and fish, eliminating felt is probably a good idea, although its not going to solve the invasive species crisis by itself, and may not do much at all. Eventually, boot and wader companies are going to have to address all the other microbe-carrying parts of their products (and some already are) or else Montana is going to have ban shoelaces. Check out Singlebarbed's writings on the subject here and here.
Assuming this bill passes (and assuming you decide to actually uphold the law), you might be asking yourself what's next? And by that I mean what is the law-abiding fly fisherman's best option in the wading boot category, assuming he or she doesn't want to end up pinned to a rock in the middle of the Yellowstone River. Rubber soles (not to be confused with Rubber Soul) are available, but most of the reviews I have read concluded that rubber soles are great most of the time, but when you really need the stickiness they are often found wanting. Unfortunately, those times when you really need the stickiness happen to be the times when not having it means you get washed downstream through a rock garden.
Maybe the current crop of rubber-soled boots are an upgrade in this department, I don't know. As someone who is currently in the market for new boots, I'd be more than happy to have Simms or some other company have enough guts to send me a pair to test out (come on, man up! send me a free pair of wading boots!). Assuming that does not happen, I'll probably spend some time this winter looking for a pair I can afford. I prefer that over crossing the entire state of Montana of my list of places to fish.
Oh, and Simms and any other wading boot company, I'll be happy to provide a shipping address, just let me know.