Way to hijack our fledgling rotary Forum Snow.... The idea is to KEEP people here!!
You asked a broad question there, but the quick simple answer is that it's about as different from FW flying as you can get. From the type of people who are attracted to helicopters, to the working environments, locations, wages and overall attitudes. That said, they do share some similarities such as the difficulty of getting that first job or two, the fight to gain experience, and the time spent moving around for work.
Personally, I've spent enough time in both FW and RW to see where I want to be, and that's in rotary. Hands down. But it's a very individual chioce as the lifestyles are extremely different. If you have a need to be in your own bed every night, or at home most of the year, maybe helicopters aren't for you. There are of course many "Base" type jobs that allow pilots to be home all the time, but as with anything, there are pros and cons to these positions. The "Pool" type situations are more common now with pilots and Ame's living where they please, and being flown to where the work is on rotations such as 28 on 14 off, 21 on 14 off, 28 and 28, etc etc.
The salaries in RW are similar when getting started on the ramps/hangers, that is crap, but if you compare a 1000hr FW pilot to a 1000hr RW pilot, RW will out earn them almost everytime. There are lots of guys in the 1000-2000hrs range earning $60-80(ish)+ per year, depending where they work, where that is extremely rare in FW. Once you become good at specialized work like Long Lining and Mountain work, you're value tends to be much higher. At the sharp end there are Heli Logging drivers making $200,000+ per year, but again, there's a big trade off for that type of money, and those jobs take years to get into with learning the skills required to do them.
Appart from a few specific outfits like Air Tindi, the Borek Twin Otter guys, and a few smaller operators flying off-strip/coastal float stuff, the major difference I see is that RW is based on flying skills, FW not so much. In a helicopter, you can either get the job done safely and efficiently, or you can't - logbook hours are less of a measuring stick. There are many jobs such as logging, siesmic, drill moving, aerial construction and rescue work, that many pilots just can't do, and don't possess either the skill or attitude/disposition to learn. In FW flying, especially the 704/705 stuff, it doesn't really matter, you can be taught the SOP's just like the next guy.
Not to say there aren't some FW pilots who are better than others, but the system makes sure the worst pilot at WJ or AC/Jazz, CMA/Georgian can get the job done. In helicopters that just isn't the case, customers won't work with you if you can't instil confidence in them, much less scaring them. Pilots are regularly "run-off" jobs like drill moves and siesmic operations.
That's a start as I see it, I'm sure other's will have interesting things to post.