My Surly (my avatar photo) has MTB bars with a slight rise on it (Forte CTR carbon bars). They're cut from the original 61cm (christ!) to 53.5cm (narrow as I can go since the shifter/brake won't slide over the bend). I have to say it feels odd switching from standard drops to risers. Not bad, just odd. I can jump from one bike to the other to feel the differences and it's just a trip trying to get used to the risers after riding on drops for a while now. Feels so..... upright and wide.

Risers have definite advantages and definite disadvantages. I'd say wider real bullhorns (not chopped drops) give you the best of both: an upright and comfortable riding position when desired along with a more aggressive position for climbs, etc.