-You won't get any improvement in ride quality. If anything it'll probably be harsher.
-It'll cost you a cool $75 extra.
-It's heavier by ~50-150 grams depending on the fork (ie depending on whether I'd use an SL steerer or standard).
-You can easily just use an adapter baseplate ($12) from King or Cane Creek and run a 1 1/8 straight steerer on your tapered headtube.
Thanks to Mike for the pics!