Just took a quick look.
here we go...
This is just a personal preference, but I *hate* damaging sectors in DM maps, unless they're being used carefully to enhance the difficulty of performing a particular action (e.g., exiting, grabbing BFG) - just having them surrounding some of main (narrow) pathways and combat zones would drive me bananas, especially in this case, since in some areas the only way back up is to lower a lift, effectively forcing you to pause while you wait for it to lower and raise - not good for a DM scenario, since it doesn't make for fast fluid gameplay.
In general, a fun DM map shouldn't present the player with its own additional challenges - it should guide the action with a light touch, allowing for a variety of different combat scenarios, primarily determined by weapon placement and by promoting different kinds of movement patterns. The map should challenge the player only if the player wants to gain the upper hand by grabbing very powerful items. It shouldn't also be something that the player is working against, as you effectively are if you're forced to spend a lot of time moderating your movement to avoid falling/damaging sectors (again, this is just a personal preference - your tastes may well vary).
A few smaller quibbles:
- You have a turning and corridor that leads only towards the exit, so a section of the map that isn't really marked off from the rest of it, but that - most of the time - the players have no other reason to go to.
- I'm not averse to doors in DM, but for a small map you have, what, three(?) here. Doors slow things down by enforcing pauses, which again detracts from fast fluid gameplay.
- Some irksome item/sector placement, e.g. the the impaled zombiman at the intersection of the bridges, and the four pillars surrounding the water pool - since these are in confined spaces, they really get in the way. Speaking for myself, in DM I get from A to B by strafe-running, and spend a lot of time effectively zig-zagging, and so if a map has a lot of stuff to bump into it's not so fun.