I clip into my Time ATAC Z's without even thinking about it (which can be a problem if I don't want to be clipped in ; ) Basically, I put my foot down on the pedal and I'm clipped in with them. SPD's were sometimes a problem to get into, for me. I highly recommend the Z's for mtb clipless if ease in and out is the issue.
With regards to using the Z's as platforms, it's 'OK'. I haven't really found any clipless pedal (and I think I've tried them all; Times, Mallets, .....) that gave me much when unclipped. I've started riding platforms with pins (Wellgo B67's) for much of my riding and love 'em. It takes less than five minutes to change the pedals so I put on whichever ones I want to ride.