After about ten sessions, my wife and I agreed on a few small issues with the games controls. While she had trouble with the jumping, specifically timing the jump up to smaller platforms, I had trouble timing the power kick, and missing with the kick felt punishing because we were left open to attack if we missed. We ended up abandoning the kick altogether and relying on the punches.
We feel that if you make the jumps a little smoother, and make the kicks more accurate and maybe more powerful, we would be more likely to use them.
Smaller requests would be the following, these are just ideas to make the game feel more flushed out.
1) An opening story screen to give us character motivation. It could be something as simple an a still image of our characters with some text.
2) The boss battle would feel more fair if we had a quick indicator to jump out of it's path. A boss power bar would be nice too.
3) After comparing SPK to Snow Bros. we thought it would be cool if the score for each kill would pop up briefly (where the character dies). This is a minor request but it would add to the feeling of racking up a high score.
Please be encouraged though because we obviously felt inclined to keep on playing. SPK is just a few tweaks away from being a classic style arcade hit.