When I switched to Firefox from Chrome I certainly encountered some bumps in the road which almost caused me to go back. A few functionality gaps (I really the double-tap to zoom to a 'block' of content), but I think the biggest thing was that some of my day-to-day workflows couldn't be exactly replicated in Firefox.

Of course, now I'm used to Firefox, and my routine is centred on it - so now when I fire up Chrome, I have the same experience in reverse.

I don't think Firefox advocates should under-play the amount of time and disruption the shift to Firefox involves: but I do think it's worth doing. While there are a few things I miss, Firefox meets all my needs and more.