Finally realized I'd been watching the wrong thread for updates on the videos (was just looking at the Round 1 thread..), so putting some thoughts together on what I've seen so far. Will do Group B first since Group A is judged and has lots of comments already.
A Fistful of Dubstep - The first few seconds of the intro had me interested; it really felt like it was building up to launch into something great. Unfortunately it didn't follow up. There was no real coherence in the scenes chosen, and a blandness in their use. The effects were minimal and simplistic, and in a way that didn't really help accentuate the song.
How it could be better: take advantage of the longer frame times. The source itself doesn't actually appear suited to sharp fractional-second edits (old-school cell-animated, rather than newer digitally animated), but would work better with more of the repeating and reversing motion actions. Also, fewer digital effects; the effects used really don't work well with the cell animation.
141db - Honestly, it was fantastic. Criticisms here are mostly nitpicky details.
I don't have any problem with the staticky effects that others have mentioned; I thought they fit in well.
While the black-and-white effect was great for impact, I felt there were a number of issues with oversaturation or overdarkening -- the brightness and contrast balances were off, and you ended up with too much pure white and black, where there should have been more grey.
Poor extraction of the hair braid at 0:43.
The repeating lips at 1:17 didn't really work, I think. The ones at 1:25/1:30 weren't quite as bad, but also not quite right. The one at 1:40 was the only lip sync bit that felt like it truly belonged there.
BANGARANG! - First, it was a great video. However there were several minor things that bugged me about it.
The video frame tracking effect (can't remember what it's called; eg: 0:19) always felt like it was about half a second behind the audio, so while the -idea- of the effect was neat, it was jarring in practice.
The central fight portion with BRS, with the text effects, seemed just about perfect.
It was odd switching series midway through, but at the same time I can't exactly fault you for it; it works, mostly.
First portion of PMMM section was well done, but seemed to lose traction a bit when you get to the part with Homura firing the cannons. Picks back up from the flared wings to the end of PMMM segment. Also, the tracking effects in this segment were much closer to lining up properly.
Bakemonogatari segment: the video tracking effect matched up pretty well this time. The remainder of that section loses too much from oversaturation via brightness effects, though.
There is maybe one drill in this entire video - The intro wasn't too bad -- I could see the point it was aiming for -- but it felt rather lackluster. Most of the rest was a solid B; lots of places things could be tightened up and improved, but nothing actually -bad-.
Fight for Love - Nice, but not great. While there are lots of cuts that move at the pace of the song, they don't actually seem to be done in sync with the song. It's like it was edited to another, similar song, and then muxed with this one because it happened to be pretty close to the same thing. That's largely the problem I had throughout the video: it just "doesn't quite fit".
There were also a few half-hearted attempts at effects that needed to be used more consistently and determinedly, or dropped as distracting.
Lost Samurai - Weak at the start, but felt like it was improving throughout, like the editor was gradually getting a better and better idea of how to make it all work. Seems more like the first pass of making the video, that needs 2 or 3 more passes to bring everything up to speed together and really be "good". Easily attributable to the time limit of the contest, but unfortunately we have to consider it in its current state.