Have spent years on clipless, but now ride mainly on flatties with either DX or occasionally 5.10 shoes. Used to switch pedals over pre-ride depending on the ride, but now I've improved my technique on flats, I can't be bothered switching the pedals over.
I've tried the 'caged' Shimano and Crank Bros pedals and found both to be a really poor compromise. Personally, I found that as soon as you start hitting stuff you need to be clipped in, as there's just not enough grip to keep your feet secure when unclipped.
Personally (and as others have noted), I think it's an either/or choice. Clipped and back off the tension, or if you do want the easy 'bale-ability' of flats – just get you're technique sorted, some decent pedals and shoes and you'll never have any problems with feet coming off pedals or bike falling away from you. (also really helps general technique when/if you do put the clipless pedals back on)
p.s. if you do want to try the caged Shimano DX spd's I can sell you a lightly used pair;)
p.p.s. if I was still riding competitively though, I'd def. go clipless , just because you can pull up for max. power – far too old and farty for that now though 🙂