I'm really curious to know why your making the switch... I work in a DB2/MS SQL mixed shop where we have DB2 LUW and on z/OS plus we have many MS SQL Servers. They all play well together for the most part.

So my question is why, and to what version of DB2 are you moving to (LUW or z)? I agree with others, the cost I'd assume is probably equal to or more, and I've found IBM support just as teeth grinding if not more so than MS support. The whole PMR process through IBM is crazy and their online support is about where MSDN was 10 years ago as far as quality with outdated info and many broken links.

With that being said I do like DB2 as a RDBMS for the most part, and though some of its methods are crazy there's some logic to most of it. Just be ready for connectivity issues until you learn the DB2/IBM way of doing it since it's completely different from MS SQL. Learn how to install the DB2 client and catalog nodes and databases since that'll be the biggest thing for clients who make direct DB calls. Also research DB2 connect of you plan on using DB2 for Z. It can be used for DB2 LUW as well, but I don't think it's needed as much on that front. Also start learning IBM Data Studio. It's their SSMS equivalent, and though it's nice it's buggy and not very intuitive.

If you'd like send me a PM and i can share more info and some of my notes on moving between DB2 and MS SQL there since they're outside of the forum scope.