This is my experience over the last two months of rebeginning to ride MTB- on a FS 29er. Before purchasing my new bike I thought and read alot about the clipless , but instead decided to do all I could to prevent slipping off of flats to start with. So I got some Five Ten shoes (Sam Hill cuz I liked the look) based on reviews of the sole stickiness etc. I have some fairly cheapo Blacklabel poly flats with pins ( that I have broken off a few of bashing rocks

). Figured if I did decide to go clipless after all the shoes are fine for daily use anyways and I wouldn't be out much on the pedals.
Now while I am technically a noob, I do ride pretty agro an hang with (or dust) some much more experienced riders especailly as the day wears on. Only once in these two months has a foot bounced off going over some roots and it was no big deal, no scraping of the shin, and didn't lose but a seconds drive time. But I have done more than a dozen very quick/reflexive "emergency" dabs at low speed that probably wouldn't have happened clippless...
My observation is that there are a couple factors many don't discuss on the flat/clipless debate- suspension and terrain. If one is on a FS, there is alot less jarring/bouncing on the pedals or at least it is dampened somewhat. Secondly, if one rides most XC on not overly rocky terrain or alot of climbing ( such as here in Florida), the bouncing potential is less also. I haven't decided yet if I'm going to go clipless yet, still need the necessity of such to be shown to me. Afterall, I'm still learning.
I expect to be thouroughly flamed on this, but to each his own :thumbsup: