Oleo: Yeah, I tried what you said but it still crashed my second instance of Q4 as soon as I tried loading it. Also, for Q3 g_sync wasn't required, it was only nice if you didn't want choppy demos. IOW, for feedback demos it didn't matter.
pjw: Argh, its so much easier to point things out in a demo, but here is some old fashioned textual feedback for you...
-RG placement - its in one of the longest stretches of the map, not good IMO. You can aim from one side of the long RG "hall" to the other, meaning it will promote slower snipey type affairs. I'd rather see the railgun in a more dangerous and cramped positioni so it isn't immediately rendered as all-powerful.
-bottom floor height - Seems like the bottom floor in some areas has a really low ceiling, is this necessary?
-low doorways - Related to this, you seem to hit your head a lot jumping through some of the doorways since the ceiling is so low
-double JP near quad - I'm not a big fan. Makes for kind of finnicky gameplay there. I'd rather see a single JP or maybe a plat
-crates - there were a bunch of crates that looked like you could jump on them but in fact you couldn't. I know this is partly due to the fact that the Q4 bounding box is taller, but I'd prefer that some of the smaller crates be jump-onable.

Also, the crate in the ladder room (I love the ladder btw), needs another small crate so you can hop onto the big crate and jump over to the ladder (as opposed to just ramp jumping to it, give the player options)
-ladder area - The L-shaped path needs a wall/fence there so you don't fall off the edge. You've got *a lot* of places where you can fall into the void, and if you're a noob player or have a bad ping this map is not going to be a fun experience.

This is one of the places where I think you need to block the player from falling. You might put walls/fences in a few other places as well.
-25h on crates in quad room - Kind of a weird place for it. You see it from below but can't grab it, and from above you don't usually think about it. Maybe make it so you can access it from below (more small crates) and maybe make it worth accessing by changing it to a 50h?
-hyperblaster - I'd say move that to the little "nook" near where the MH tele dest is (currently has rl ammo and shards I believe). This will make for much more interesting battles in this area because the freshly spawned players will have to go into the nook to grab a good weapon.
-JP triggers - In general the JP triggers were too high, so it looked like I was never actually touching the JPs when being propeled. One time, upon killing my opponent he even dropped his RL onto a JP and I couldn't grab it b/c the trigger brush was so high, lol.
-MH room JPs - These were very confusing for me. I know you're trying to do something different w/ them, but the confusion combined w/ the void right near them was not fun.

Not sure what you can do, maybe remove the void? Also, after dropping down one JP chute and getting propelled forward, I kept on wanting to strafe jump to the opposite side JP and take that up, which I know you can't do but still.
-edges of level - The edges of the level (like the side panels of the map) that touch the void were all pretty bland geometry-wise. Is there any way you could add some detail to them so that you at least have something purty to look at after falling to your death?
-overlapping brushes - Not exactly sure where this is at (*cough* b/c I can't record a proper demo :P *cough*), but somewhere on the lower level if you looked up at the ceilling there were 2 overlapping light brushes I believe. They are pretty easy to spot and I'm sure somebody else will screenshot them if you can't find them.