I switched from a 12-25 to an 11-32 for some road rides this summer. It accomplished what I wanted, which was to get my sorry butt over some big climbs, but on the whole it slowed me down. The reason is that when you shift up, it drops you outside the efficient cadence range, and you have to work hard for a few seconds to get back up to a good spin. And it does that for every shift.

The questions you need to ask yourself are, (1) how often are you going to use a gear with more than 25 teeth, and (2) is it worth having to use a long cage derailleur to get that?