Greetings:
I'm actually fairly new to this myself - only working on my second campaign and not very well versed in the nuts and bolts of the game. "Flybert" hosts a forum (swwisa) that has modding members. I haven't even used any terrain mods and have not been using a glide wrapper (I marked "windowed" in the graphics section). I have (or had - one of my dogs grabbed the disc from a table) the "full canvas jacket" patch - not available free and super expensive for an elderly patch - but I never was able to get it to work. I'm told it is an excellent patch and others have gotten it to work (I believe) with the gog version. Actually, I think the only difference in the gog version is that there is no disc needed and the official patch is pre-loaded. I've been using the "Hell's Angels Super Patch" and have been happy with it. Next go'round, I'm going to use the CM11 system (as soon as I find out whether or not it is an actual mod or is compatible with the HASP) to start the game a bit earlier in time and hopefully to correct some of the ahistorical planes being used (for instance, Jasta 2 was formed in Sep 1916 and used mainly Albatross planes (one original was a Fok D-II) but in the game, it uses the by then obsolete Fok E-III).
There is a program provided (RB3DXPFix) that needs to be used if you are using XP (maybe Vista and 7 too) that fixes the sound and needs to be used to start the game every time but I don't believe that involved distorted sound (missing sound, I believe).
I've been enjoying it - the makers really did pay attention to the history for the most part and the AI generates missions randomly so similar missions are never the same.

Thanks for the response lordhoff, I didn't know there was any sort of XP sound fix. Perhaps it was because it was 2am when I posted that I got a little muddled, Wailwulf seems the most historically versed in this game.
I'm excited to try out some patches, especially terrains and new plane models, but I'm not sure how exactly to get them to work. You say the Hells Angels patch is working well for you? How did it change the game compared to its original styling? Is it fairly straightforward to apply to the game?
I've not tried to get into a campaign online or anything yet, I'm still trying to get a feel for the plane mechanics, but I think I'll have to try someday to get in on a group game. Hope to see you out there!

The HASP is fire and forget - just load it and start. It did nothing to the terrain (I'm told terrain mods can be added) but the planes are upgraded in both historic looks and how they fly. I added it very shortly after starting so I'm not sure here but I believe there are some additional planes too. Some less major aces were deleted and replaced by more major ones. Photos and music were upgraded/changed.
Unfortunately, my only option for I-net is via a satellite link which is incompatible to any on line games that aren't turn based - there is a long delay as the signal travels to the satellite and back to Earth then put into the net. There are sites (possibly swwisa) that list active squadrons and many appear to want new members. I believe one is a sort of mercenary squadron that supplies pilots to others that are short. I'm not sure how they do it with so many game sites having shut down - perhaps with a remote LAN like Himachi? Also, since the gog version has no disc and host sites sense this and disallow your connection, you'll need a workaround. Wailwulf has posted the details here (somewhere :) ) but it is simple. Once some code is changed, one has to click six times on a particular icon (the original game was like that) and one can get on the sites without a disc.

SWWISA is more single player based then multi-player. Wings of Valor http://www.wings-of-valor.net/ is where a number of the Multi-players go and lists the squads, though most are defunct. My squadron is First Aerial Battalion http://rnas.hostei.com/index.php, Currently most of the older members are now getting into Rise of Flight, but we are still RB.
The servers are hosted by players and through the meta files, they can be seen by other players. To get the current listing of Meta Servers to put in your mplayer.ini file can be found here: http://sites.google.com/site/metaservers/ All of the servers that Gog added to the mplayer.ini file are defunct or obsolete.
The home brewed security software that server operators use does not like GOG's version of RB3D. GOG tweaked the code so the CD would not be asked for and the security does not like it. Sierra had written a work around for the no CD problem, which was the clicking on the right upper cross six times to get the game to run. This requires a stock, unmoddified version of the Baronmmp.exe that has been patched to version 1078 (the last official patch by Sierra). I host such a file here: http://cid-e196374a237958b4.office.live.com/self.aspx/RBFILES/Baronmmpexe.rar This is just the Baronmmp.exe patched to 1078.