Hi Wade,
I'm working right now for a client who has everything on WAzure. AzureStorage for everything like images, pdfs, etc, AzureTables to store emails, SQLAzure for all the application relational data. We use the API assemblies, not the REST API directly, but it's likely the same concept.
Working with LLBLGen+SQLAzure is very easy: you make your project against a local SQLServer DB, then for production you just change your connection string. If you are going to generate EF, then it's a matter of EF, but I'm sure it will be no problem with that.
Probably you will use AzureStorage+SQLAzure to store reference to your files in your tables. You just have to store the AzureStorage file uri, then use the (dll/rest) api to download the bytes. So basically is like a normal app, it's just that the stuff is somewhere else.