I concur with Maria. George Orwell gave "twenty rules for stylish written English". Number two: Prepositions are not words to end sentences with. Number twenty: Ignore any of these rules rather than commit a barbarity. If Orwell can do it, so can you and I. So, it depends. If it feels right do it. If it looks (or sounds) ugly, recast the sentence.

The shortened construction has been standard US form for many years, but is being seen more often in Britain nowadays especaily in quality papers. I'm still not used to it, and usually have to reread the sentence in which it appears. For me, this detracts from the pleasure of reading perhaps an otherwise interesting piece. But I guess that's what called progress nowadays. Bottom line: the shortened form is not yet standard British form, but it's getting that way in papers at least, if not in the spoken word. I for one regret this change.