Grug wrote:No particles?
What does that do? ...besides the obvious.
I'm curious myself, since it doesn't seem to be in the D3 readme.
As for what to expect...well, if you haven't played Descent at all before (or even if you have

), here are one or two pointers:
The controls can be set up in any way that you so desire. The most important thing to remember is that the Descent series is all about six degrees of freedom, so you'll need to be able to pull off several different types of maneuvers at once. The ideal config should allow you to turn left/right, pitch up/down, bank left/right, slide left/right, slide up/down, and move forward/back, as well as use the afterburner, all without any significant movement of your fingers. Just think of it as Freespace with the addition of sliding and moving backwards. Any person you ask probably has their own unique setup, with the most popular being joystick/keyboard; mouse/keyboard is another frequently-used one. I personally use a joystick-only config, with the hat switch used for sliding and the throttle for moving forward/back. It's really all about what feels right for you, so don't be afraid to experiment. You can access the controls config from the Options submenu on the title screen or by hitting F2 in-game.
As far as expectations go, don't expect to be absolutely blown away by graphics; D3's about as old as FS2, and we haven't had the benefit of having the source code available to fool around with. Still, it's not as though the graphics are incredibly archaic; they're certainly much more modern-looking than D1/2. As far as singleplayer goes, if you're interested in that, you'll probably be presented with a cutscene or two that doesn't make much sense if you've never played the first two games. (If you do want any details, just ask.) The first time you play SP, you'll be presented with a training mission that walks you through the default control scheme; it's pretty useful for getting used to how things work. The actual SP gameplay consists of blowing up bots while trying to complete certain objectives in each level. You're right about remembering outdoor areas; unlike its predecessors, D3's Fusion engine allowed it to blend room-based and flight-sim engines seamlessly, so there are both indoor and outdoor areas in-game. Just remember to hit F4 for your Guidebot, Tab for your automap, and Shift+Tab for your mission objectives and briefing recap, and you should be fine.
As far as multiplayer goes, just like Freespace, D3 used to use PXO as a server list. Unfortunately, we weren't able to create something like FS2NetD as a replacement. However, there are still a number of ways of finding TCP/IP servers. The one I'd recommend is called
Vortex; it's a fan-made program that has a built-in server list and allows you to auto-download levels; it also has an interface for joining D3's IRC chat channels. As far as multiplayer gameplay goes, it's pretty much your standard modes: Anarchy is deathmatch, Team Anarchy is team deathmatch, CTF is, well, CTF. There are a few unique modes, though; Hoard and Hyper-Anarchy involve grabbing orbs to score points, Monsterball is a football-like game (see, I even called it football

), and Entropy is a rather complex but sadly under-played mode involving using viruses to capture enemy bases.
One thing you'll have to do before going online is choose your ship, which you can do from the pilot selection config menu. The Pyro-GL is pretty much good all-around, the Phoenix is light on shields and weapons capacity but big on speed, and the Magnum earns its nickname of Tank from lots of shields and weapons capacity but slow speed. There's also the Black Pyro, which is only available with the Mercenary add-on or a separate patch. It's really up to personal preference which ship you use; fool around with each one to decide which you like. Oh, and don't get discouraged if your first multiplayer experience ends with you getting your ass kicked; Descent has a very high learning curve, and some of the players out there have been playing since the first game came out, some eleven years ago. You'll start catching on soon, though.
As far as mods go, there wasn't a big D3 modding scene, and the mods that were made aren't played too often. You might see a game of
Pyromania once in a while; it's the closest D3 has to a full conversion, with several new ships and lots of new weapons. Other mods out there every once in a while are Instareap (like Instagib from the Quake series), which features everyone using the railgun-like Mass Driver for one-shot kills, Dual, which sets up one-on-one matches in isolated rooms, and Frag-tag, which uses the shrapnel-spewing Frag missile in a game of Tag. You can find all of those, along with ship skins, miscellaneous mods, and a massive D3 level database, at the link that Hunter posted.
I think that's pretty much most of the basic stuff. I've played and loved this game for five years, so pardon me if I got a little wordy. Hope you enjoy your trip down into the mines.

A.K.A. Mongoose, for you HLP denizens