Couple of them are Ruby, I didn't really want to install Ruby so I didn't try them. Here are my comments (don't expect any kind of system, here):
Lucentbeam - This entry had a cool visual vibe, I like the clockwork look and theme. But the controls seemed wonky and confusing. Left and right didn't map directly to counterclockwise/clockwise, but instead seemed to toggle. If I pressed left once, it would go clockwise; press left again and it would reverse. Same with left. They seemed to switch meanings, and it confused me.
crow007 - While it doesn't look like much, it's actually the one I played for the longest. Ball speeds seemed kind of unpredictable.
Noctumus - Very smooth, very fast paced. A little too fast paced for my slow, creaky old reflexes. It looked decent, played well.
wintertime - Didn't play.
vortez - I really liked the updated/traditional look. True to the original, but with a modern upgrade to it. Played fast and smooth (again, a bit too fast) but the predictability was a snag. Ball always launches at the same angle. Of course, given the disparity between the ball speed and paddle speed, this is probably for the best.
shadowisadog - This one was pretty basic, visually. Biggest issue I noticed was that it ran very roughly, as if no smoothing or interpolation were being done on the ball movement. Made it very difficult to play for more than a few seconds.
segmented - Loved the style and look of it. Theme was pretty cool. Biggest issue was that the "splash" or explosion the ball makes when hitting the walls made it hard to know if my paddle was lined up on the ball properly. Made for a confusing play experience.
ml_ - Didn't play.
staunsholm - Didn't play.
mippy - "Hot balls!" This one made me chuckle, when I got the "Hot Balls!" message. Was a little bit confusing to know what was going on. I sometimes got blown up and wasn't sure why.