Yeah, I really enjoyed Unit 13. Like many folks said, it was a portable, less extreme version of The Club. When you got your 'racing lines' happening after a few cursory runs through a level, it was incredibly satisfying.
I found RCR a little joyless. It should have been a lot more exciting than it ended up being. A little too much fan service and too little meat on the bone. Perhaps not the right way to look at it, because it was pretty hefty in content...just not spicy or tangy enough.
Nah, it's more like a puzzle platformer. The weapons are pretty satisfying for the game it actually is - great audio-visual response to fire - but it's a lot slower than a Contra or Metal Slug. Only two forward firing stances - standing and crouching - if that helps describe the game a little better. Not counting the flying sections. Personally, I like the platforming much better.
For ten bucks, it's pretty good. For the Plus discount, it's money well spent. It'll probably end up a freebie for Plus subscribers, so if any doubt remains, see if a demo pops up or just wait it out.