Did any one you completely change the area of chemistry they work in? How did it go?
I've changed my area of interest (dramatically) multiple times. I started out in computational chemistry, then switched to inorganic chemistry when I went into grad school. Ended up doing mostly time resolved spectroscopy for my PhD work, with a little bit of synthesis to prove to myself I have no interest in it.
For post-doc I went to nanomaterials and microscopy for two years. Then I completely lost my senses and now work with composite plastics, environmental science, and packaging for my full time job (not in academia). There is a small link between each of these steps so that it's not quite so illogical as it sounds, but still each time it required me to abandon a lot of what I already considered myself an expert in and learn something completely new. The down side is that you feel like you are starting over again a lot and you may start to have the reputation of a jack of all trades (and a master of... well you know). But on the other hand you'll find it makes you a very well-rounded scientist, continually keeps things fresh and interesting - and you'll be surprised how often those old skills prove useful in areas you didn't think it was possible.
Personally, I like reinventing myself every now and then. For the same reason, it's good to move to a new house every few years. Let's you get rid of all that junk you've accumulated over time. It's how you stay young and invigorated.