I presume you’ve seen the feature comparison on the Pro version vs. others. http://world-machine.com/download.html (scroll down a bit) Admittedly there is not much information besides this, but the features outlined in the comparison seem to form the basis for a solid Pro version. You have automation (very powerful), multi-threaded building which would of course significantly increase build speeds on multiprocessor computers (and possibly P4 HT’s), and perhaps most significantly for game development the tiled output functionality. I am sure more details on the Pro version will be discussed when it is closer to being available for actual purchase. 
I don’t know specifically why Stephen wants people using the SDK to provide an e-mail address, but it doesn’t seem to be an unreasonable request at all. SDK use is a non-basic type of feature, for advanced users only. Those are the kind of people one would expect would purchase the Standard or Pro versions. Not providing an e-mail address seems like an unusual need for someone that interested in the program.
I am sure you have your reasons for not having e-mail, but with the myriad of quality free options out there it seems like little burden to get one, even if it’s only for this purpose. I am sure that there have been other instances where an e-mail address would have been handy for you, and surely if you’re creating a game for public consumption you’ll eventually have to get one anyway. 
I agree that the number of generators in WM is limited. However the Perlin does feature 7 different variations, and there is also the Voronoi generator that has a tremendous number of variations. Although the actual number of individual generators is small, the variations possible is fairly large, especially in combination with the other devices. I am hoping that, with the PDK being now available, new generators will be created by the community.
Ultimately I think if you are not satisfied by the Basic version of WM that is freely available, and the features outlined for the Standard or Pro versions do not seem to be enough to sway you, then WM probably isn’t the tool for you. But keep in mind you can program your own generators and affectors if that’s necessary for your project. Take a look at the Lego filter that Fil created for example. It is simple, but it also took him very little time to create. I think it is clear from this example that the SDK is at least very easy and quick to use. The power and flexibility is an unknown until you get your hands on it, but I’m sure Stephen will work out an alternate contact if necessary.
But if you know the algorithm behind the generator, making one is easy. My Lego Filter took me a few hours to get the rough thing going on one tile, then the rest of the week to polish every other detail not related to the algorithm (choice of parameters, UI, explorer behaviour, etc)…