The Good: Nice and light with a great geometry. Feels at home at skateparks and on dirt. The 21.2 TT combined with the short back-end makes it nimble and great for manuals but still roomy enough for long legs and wider bars.
The Bad: I'm yet to find a negative with this frame. If I had to pick something, one of the welds isn't perfectly neat, but the weld isn't done badly, it's just not flawless.
The frame is built up with mostly Mutiny parts. I've used the frame, stem, forks and sprocket and they all went together perfectly. I worked in a bike shop for a year and this build was one of the smoothest and tightest I've built. That's always a good sign.
The frame is light yet feels solid, feels nice at skateparks and on dirt. The 69 degree ST angle is a nice idea... It keeps the front long and leaves plenty of room without turning it into a limo and the short back end keeps it snappy. A 'best of both worlds' situation.
I run the axle half way in the drops, so the back-end is 13.5". I wouldn't want it any shorter than that with the 21.2"TT... I think it would start to feel unbalanced, but that's just personal preference.
I haven't run pegs on the Cosmo yet and I never do anything more than the odd peg-stall on coping anyway, so I can't provide any information for hardcore street riders...
The guys at Mutiny are legends too, I emailed them to let them know how I felt about the frame and parts and Gaz got back to me first thing in the morning to let me know how stoked they were that I was happy with their gear.
The Cosmotron is great frame, (and that green is awesome too) the Mutiny parts are brilliant and the communication from Gaz and the team was excellent.
If you want to support a down-to-earth, rider-owned company who sell interesting, quality products, I think Mutiny are worth a look.