Do you play the alto flute, or a soprano flute (what most people think of when they hear "flute" is a soprano)?
In any case, it's quite a quite different, but not impossibly so. It'll take you some time and practice to get used to relaxing your embouchure enough to diffuse the air in such a way as to produce a good sound, and to figure out how to adjust pitch, tone, etc. However, there is very little call for bass flute players outside of flute ensembles, so if you intend to play seriously, I would encourage you to keep your C flute chops up, rather than switching entirely (that is, double rather than switching).
I play a Jupiter 523 bass flute. It was kind of difficult to get used to at first, but now it's not too bad.
One thing I miss is that the 523 does not have D and D# trill keys. I can still get by with using harmonics for most trills. The trill keys would come in handy to improve the tone of middle D to E, however (at least they work that way on my alto flute).
Also, high E is quite difficult to produce consistently. The 523 does not have a split E, which might exacerbate the problem. I have no problem hitting high E's on my concert flute (Pearl 765 Coda), which doesn't have a split E either. I guess it's just more problematic on the bass flute. I've tried several of the recommended alternate fingerings, but none of them seem to help. With practice, I'm getting better at it, but it's still about 75/25 whether the high E comes out or not.
If I had the money, I would have bought the diMedici 1123 bass flute, which includes the trill keys and a split E. As it was, I got a fabulous deal on the Jupiter 523 (like new demo model for $1299), so I'm not complaining. It suits my purposes.
Of course, if I really hit the jackpot, I would go for a Yamaha or Kingma bass flute.