The MS Marketplace has been there for many months, and there are some things which I think might improve the user's experience and developer engagement.
1) Allow to tag some files, chosen by the developer in the SDK editor, to be left unencrypted, this is likely the most important requirement, for many reasons, like being able to offer QUICK fixes ( usually the airport definition .BGL gets updated more often ) to users as a separate download, or allowing other utilities to read the file, without having to wait for an API to get the airport data from the sim.
2) Handle dependencies with a proper documentation. Lots of developers would like to optimize and reuse their own libraries, but it's not clear how this will work in the Marketplace.
If I have a certain library that is ( or might be ) shared between several products, is this library supposed to be included in every package ? What if a subsequent product will come with an updated version of the library and, most importantly, what if the newer product has been bought on a DIFFERENT platform than the MS Marketplace ? Does packages in the Community folder always take precedence over the ones in the Official folder ? Are they all merged as one ? Using which order ?
3) Allow alternate versions of the same product, to be installed at user's choice, that are not supposed to installed together, but are still part of the same purchase. For example, we just released a Mesh product in two versions, with the one using a lower resolution being a better choice for performances, depending on user hardware. Each one is a separate package, and they are not supposed to be installed at the same time, but the only way to achieve this on the MS Marketplace, is to create to separate products that should be bought separately, since it's not possible to choose between two variants of a product in the Marketplace.
4) Offer a way to check if a certain product has a valid license. Without disclosing any customer data, of course. This way, installers/updaters can offer updates to licensed users as soon they are available from the developer, without waiting for them to be released on the Marketplace. Lots of users are concerned of the time required to approve a release, possibly resulting in loss of confidence buying from the Marketplace, which we all know might not be good for the long term.