If you call providing games in their original format "slapped together" then bring 'em on.
GOG isn't here to provide third party ports, open source or otherwise. While there are some great ports out there that improve the graphics, sound and gameplay of their original counterparts, GOG's remit is (and should always be) focused on providing classic games as they were originally released, not to function as a portal to the modding community.
If you prefer source ports to the original game, then so be it. Play those instead. No one's forcing you to download a game you don't want to play. While there's very few of us that wouldn't want greater visual fidelity in our games, it's important -- especially from a cultural perspective -- that classic games be preserved in their original format as much as possible. Besides, I'd much rather play something like System Shock in its native 640x480 resolution, complete with 8-bit textures and sprites, rather than an HD-enhanced extravaganza. (I can play BioShock if I want that particular experience.)
Long may GOG continue to release games in their native state (XP/Vista compatibility tweaks notwithstanding.).

raahsnavj,
just answer me one question: What is the source of the game code good for if you don't own the game data? Alright, you can pirate it somewhere, but if you did that, why rant about GoG.com anyway?
Btw, the best available Descent 2 source port is D2X-XL (yes, I am biased, but yet ...).
You sure knew why you turned off voting for your post, it would probably be resting in the center of the earth by now if you hadn't. :P

I would think the best thing to do would be buy the games from here (if you don't own them already) so that you have the gamedata (legally.) Then download the source port of your choice and game away.

Off-topic, but what I seem to have noticed is that if the topic is started as a "comment" (blue circle), then you can't vote on the person making the comment. What I can't figure out is how you start a "comment" topic in the first place...

raahsnavj: I too prefer Rebirth to D2-XL (I really love Rebirth btw), but your comment and rating is really OT. You need to own game to be able legally use game data with source ports anyway. You are not allowed to distribute parts of the games either :) And lastly - by offering the whole game, you are giving people choice - there are some who prefer to play in DosBox, or even purists who want to play it without any modifications.
I haven't bought Descent on GoG since I already own collectors' edition of D1 and D2 for years, but I definitelly would otherwise.
I presume (and hope :), that by "slapped together" you basically mean that there is no info about those source ports? Well, it would be nice idea to add links and tips for possible source ports or fan made patch / mods with comments - basically some sort of 'wikifiable' 'stuff' :)

IMHO, that's what the forums are for! :D

This game rocks and any way to get it to work on Vista is awesome.
I don't mind paying a bit of money to get that service done for me and to guarantee support and infinite downloads.

I want to add that I prefer to get the unadulterated DOS version of these old games, as I like to try the game on my DOS-based PC that I have set up specifically for old games. While it's true that I usually play it using a modern source port later on, it's nice to experience the game as I originally remember it. I don't see anything wrong with GOG selling the original game in a DOSBox wrapper. In fact, that's what I expect from GOG: the original game, not a buggy third-party source port.

AFAIK, when Parallax Software released the source code, one of the terms in the EULA forbade commercial use of the code, including distributing the game data with a source port.

You'd be correct; my copy of Descent 2 CD works just fine in Windows XP straight after the install. (not sure about Vista)
I wish I had Descent 1 CD, to see if it had a Win 95 exe to it. If not.... There's always the source ports.