My CoFounder and I were both .Net developers in the past and love C# and SQL Server. We are happy with the Azure platform so far. We're using a little bit of everything too. Worker and Web Roles, Queues, Table Storage and SQL Azure. I'd be happy to answer any questions you have.
But, there is now something called 'Federations' coming out for SQL Server which will let you automatically and sometimes magically shard your data across multiple database with little maintenance. I'm not sure what the roadmap of that feature is but it eliminates any of the GB cap worries that existed before.
The biggest surprise we ran into was the cost of Transactions. Even though you get 10k storage transactions for pennies, it does add up. Especially since every request for items from a queue is a transaction. So a lot of thought has to go into things to make sure parts of the system aren't too 'chatty' when it comes to Azure Storage. You don't have this problem with SQL Azure. There is no transaction cost, only the GB used.
Our company deals with lots of data and real-time responses so we push many of the existing features to their limits. We haven't really had any blockers that didn't have some sort of reasonable work around. And most of the time the next release of features will eliminate a good chunk of those.
We're pretty lucky in that we're part of Microsoft' early adopter programs and get to peek at some features coming down the pipe soon. There is some awesome stuff coming, but of course we're under NDA.
There are some extra things to consider but they are more a result of using the Cloud in general. For example, it highly recommended that you add retry logic into your code which makes sql queries. This is because your data is triple replicated and fail overs or db moves can drop your pooled connections.
Also as I mentioned in my other comment. There are some limits to Table Storage which you need to account for or you'll find yourself stuck and frustrated. Things like Count,GroupBy,Joins,Distinct,etc are not available. For those familiar with NoSql db then this is no surprise. But if you're a hardcore relation guy like I was then this takes getting used to.
We're pretty happy with our decision to use Azure.