<p>I have been interested in database developing for some time now and decided that MS SQL has a lot to offer in terms of T-SQL and generally much more functionality (not saying that Oracle or Postgres don't have that).</p>

<p>I would like to know:  </p>

<ol>
<li>What are the big paradigm changes I
should expect to see? </li>
<li>How much effort do "regular" companies put
into developing their database (for
transactions, triggers, events, data
cleansing, ETL)? </li>
<li>What can I expect
    from the inner-workings of MS SQL
    developer teams and how they
    interact with the .NET application
    developers?</li>
</ol>

<p>I hope I have phrased my question correctly. I am not very clued-up about the whole .NET scene.</p>

Can't answer #1 as I've never worked with mysql but I'll take a shot at #2 and #3.
This tends to depend on the size of the database and/or the size (or professionalism) of the company. Companies with large databases with many users spend a great deal of time indeed making sure that the database both has integrity and is performance tuned. They woudl lose customers if they did not. We have 6 people who do nothing but ETL work and 5 dbas who tune and manage the databases and database servers as well as many many developers who write t-sql code.
As far as #3, in good companies these people work together very well as a team. In bad companies, there is often tension between the two groups and each uses the other group as a scapegaoat for whatever problems occur. I work with a bunch of great .net developers. They respect my database expertise as I respect their .net expertise and we caonsult each other on design issues and tuning issues and in general any issue that needs input from both sides.