I suggest not supporting companies you don't feel deserve your money. There are *plenty* of other games to play out there. And for us primary/preferred Linux users, there are plenty of companies who support you. Give them your money.
My understanding is that the delay was simply a question of priorities. Like you say, SteamOS/Linux users are a very small %.
As for whether Larian "deserves" my money...... I don't know. I do know that they'll have "earned" my money when the Linux port is done and released.
I don't think too many gamers choose not to play a game as critically acclaimed as D:OS over such issues as how delayed the game is. I've waited a lot longer for other titles and been (I'll wager) much more dissapointed in the result.
