The Marketplace team has just announced some more details around the 'Windows Marketplace for Mobile', which I think is great news:
A: No, if your application has been previously certified and published in the catalog, you can submit subsequent updates without incurring any additional fees. The application update will be made available through Windows Marketplace to all customers that have downloaded your application in the past.
A: Yes, we originally communicated that only application updates submitted within 7 days of their publish date would benefit from a free submission. After talking to the developer community and better understanding the dynamics and frequency of application updates, we have decided to extend the original 7-day window and make it permanent. This means that if an application has been previously approved in the marketplace the developer can submit updates to it without incurring any additional fees.
We hope to get a good FAQ around the Marketplace up on the developer.windowsmobile.com site ASAP, so hang tight.
Also, expect more details in the coming weeks and months around this at developer.windowsmobile.com...