Re: Arena Map Lab
It feels a lot more interesting to move around the overall space now as there are more places where you get a choice of different areas to move into, but I still think you have quite a lot of 'dead space', sections of the map that aren't really doing much.
Guys still seem to bunch up in certain areas rather than being spread more evenly. You can circle the map and stop in the biggest lab and literally wait as long as you like while you reload etc., no-one will come to bother you. (A particular shame with that room which looks like a good combat environment) Do you have big groups of spawners in some areas that need to be more spread out to other parts of the map? Better overall though.
This seems to be a leaked compile? I normally noclip outside maps after the first play to give me a better idea of the layout, but here I found I was staring at unlit exterior faces of brushes. You must always fix leaks, leaked compiles don't get vised so their performance will be shabby because the whole level will get drawn rather than just the stuff you can actually see. Arena maps can get a bit chuggy towards the end of a round in the best of circumstances because of the sheer number of dropped ammo clips etc. that will be lying around, I did wonder why I was getting so much chop while playing. If it's leaked it's also a big part of why your BSP size is so much bigger than the first beta, all the lightmap data gets stored as textures inside the BSP, and all the black outsides of walls adds a fair bit to this.
In the small lab with the Do not ingest chemicals sign, it looks like you might have two tank props in the same place? There's some weird z-fighting or something going on on the glass bit anyway.
The redesigned megahealth secret area is much cooler I think. Some good use of decals/overlays to break up your surfaces too.