I use Candies pedals. The tension is not adjustable as it is on some other pedals, but they do sometimes have interference with the tread on the bottom of your shoes. I had one pair of shoes I had to cut a bunch of the tread off around the pedal or I had major problems clipping in, especially on the right. Very frustrating, I agree! The shoes I use now (Keen Commuter Sandals) I didn't have to cut at all; they work great with Candies.

Speedplay Frogs are very easy to get into and out of, but you shouldn't give up on Candies so soon; they are great pedals and will get easier and easier to use over time, assuming you aren't getting interference with the tread of your shoe.