Walter, right off the bat, MySQL does not support CTEs for recursive querying, and it's XML support just pales in comparison to what Microsoft has.

There's no PIVOT, and no ability to APPLY results of a table-valued UDF.

There's also no ROW_NUMBER function for ranking, which will make server-side paging of result sets much more difficult.

There's more, but I think that's enough.

MySQL in general is behind most database vendors. It was only about a year and half ago that they added support for stored procs and triggers, and it took five versions to get to that point. MS SQL is more mature, in every significant sense. There is no reason to believe that MySQL will catch up to what Microsoft and Oracle have.

Also, I've read posts on web forums where people complained about MySQL deviating much further from standards, compared to other products.

I think if someone comes into MySQL without ever having used MS SQL or Oracle (or any of the other big players), they might be fine with it. But anyone who has done serious DB development with an enterprise tool is not likely to be happy with MySQL.