First, a quick note in the previous comment - The configuration option is -Duseithreads (with an 'i'). Easy mistake and I think the configure script will pick up the miss-key, but nevertheless something to point out.

Second... assuming you do re-compile a new Perl with the -Duseithreads configuration option:

Installing a new DBI::DBD under your new libraries will almost always (though may have been fixed in recent versions, sorry if so) throw a warning noting you should not use threads in a production environment. Something along the lines of:

*** You are using a perl configured with threading enabled.
*** You should be aware that using multiple threads is
*** not recommended for production environments
[download]

I wouldn't worry so much about this. It's a relatively bold statement in the first place to say this, particularly when the Perl thread tutorial says otherwise.

In any event, take the warning as you see fit; just wanted to let you know what to expect when installing the new modules.