For me, the difference was similar to weighted vs unweighted piano keys. With a mechanical keyboard I could get into a rhythm that I miss when working on a bubble-type keyboard. I've since trained myself (mostly out of necessity due to travel) to type almost as quickly and error-free on my laptop keyboard, but I do still miss the feedback from mechanical springs.
If I did 'spring' for a new mech keyboard now, however, I'd find the quietest one I could get, that still provided some sense of feedback. I don't need my noisy clicks to provide a juvenile signal to my coworkers that, yes, I am indeed working really hard on something really important right now.