The day is over now so you can shut up!!
Aaargh. I just played The Bitchin Levels again and have thus been driven crazy by its replacement sound effects. Executive summary:
There's not much point in describing each map separately as they're all quite similar. Designed for co-op so there's plenty of room so players don't get in each other's way, and that very characteristic "two or more corridors between each room" design. Yes it's mostly simple rooms and corridors, it dates back to 1995 or something although the version in the archive is a compilation with tarted-up lighting. Map05 has this cute trick with teleporters to simulate land mines, and maps 7 and 10 are enormous. Map10 is probably the best one in fact.
There are a few replacement textures which look to have been created in a very very simple drawing program. Doors with "Intruders will be shot on sight!" written on them in naff pixelly fonts, that sort of thing. It's mostly just a hodgepodge of Doom 2 textures though, vaguely tech/industrial for the most part although there are bricks, marble and hellish areas, it's pretty much a mixup.
As I said it's supposed to have had its lighting improved, which means there are a lot of sectors with flashing lights, a few sectors for light casting and surrounding lamps and stuff. It's nothing amazing, it looks like a mid-nineties map which is what they are.
Gameplay is fun though. Plenty of ammo and room to move. Easy too, you can do a maxrun of all 10 levels in two hours (I just did) and each level is fine from scratch too. I could have done with a few more rockets maybe but you get quite a lot of cells, there's less emphasis on the shotguns than most Doom 2 wads.
The only thing left is to mention the sound effects. Its author is clearly a huge popular sci-fi nerd as he's put in all kinds of Star Wars and Star Trek samples. Most of these are fairly obvious, transporter beams, laser blasters, doors etc. The most memorable are the zombies who go "There's one, set for stun!" or Riker's repeated line "Red alert!" or the alarm siren thing from the Enterprise when they wake up. By far the worst is the death sound, Worf's "It is a good day to die, but the day is not yet over". After 10 levels of this you're like "No fuckhead, it is over now, shut up"* And that's not even mentioning when you are pressing on walls looking for secrets and Han Solo goes "you can't get out that way" over and over again.
This is the first PWAD I ever played so I have a soft spot for it and play it again every couple of years. Your mileage may vary. Without sentimental value it isn't much by today's standards. You may enjoy the opportunity for fast-paced gameplay and not having to worry too much about health and ammo. You may wish to delete some of the resources from the wad before you do. Or you may wish to have a life; either's good.
* okay I admit I searched Memory Alpha to find out which episode it was from. If you listen carefully you can hear a click in the middle of the sample from where the name "Duras" has been cut out.