So Microsoft Revealed their plan for the WM7 marketplace
Developers will pay $99 every year which will allow them to post:
a)up to five free apps with every free app past that amount costing an ADDITIONAL $19.99 annually.
b) Unlimited pay apps
This to me seems opposite from how it should be. "Dear developer who makes no money from your software pay us more than developer B who makes money"

As with all the other marketplaces (Android, WebOS, (cr)apple) Developers can name their own prices. No $ limit was given but I expect it to follow more with WebOS ($99.99) as opposed to Apple ($999.99).
Developers can create Push notification service, but the article I read didn't clarify if that meant Push Notification like the iPhone has where any alerts set in the phone need to go through a third party server, or if it meant Push notifications for Updates.
Developers will be able to Unlock a windows 7 phone if they have a Marketplace account.
Unlike WebOS (which has none, save a separate "trial app") and Android (which allows returns before a certain time limit is reached), Window mobile will allow a trial period to be built into software. This will be carried out via a special API for trials.
Apps can be freeware, ad-supported freeware, payware and "freemium" (free app with option to buy extra levels/features)
There will also be a "distribute to limited users" beta interface.
More for further articles I found
Revenue Sharing will be 70% Developers 30% Microsoft
This makes the $19.99/app additional make a little more sense.
If any of you budding devs have any interest: Microsoft as a number of down loadable guidelines at
http://developer.windowsphone.com/I'll probably get bored and read/post more soon.