I have to agree with EN on this one. I used to DM exclusively, and then I transitioned to player. After I became a player, I found that I had time to work on a netbook. The netbook got the attention of Thunderhead Games, and now I write for them. In no way would I have the time to be a DM now that I write for TG. That being said, as a player my purchase decisions fall into two categories:
1) something I can use as a player
2) something I can use as a DM in the future because it's just too good. This will
always fall into the world generic category.
For example, I would probably never buy anything for the Scarred Lands setting, simply because any game I ran would exist in the Bluffside world. I have no need for any SL stuff. Do I think it's good stuff? Absolutely, I just don't want it- too world specific for me. But, I bought Bastion's Alchemy and Herbalists book because it has a lot of good ideas in it, and I can use it both as a player, and as a DM in the future. Chaos Magic by Mongoose was the same way. Both are excellent books, and both add value to me as a player, and as a possible DM. I'm going to get Common Grounds because I believe I can get value from it as a DM in the future, and because I'll be sharing a booth with Jeff Colledge this coming weekend at
FlatCon and I can get him to sign my copy.
I also own the FRCS, because it is an excellent book, does have some really great crunchy stuff that I can use as a player, but I'll probably never use it as a DM since I don't DM in FR.
But I think the DM/player thing is kind of two sides of the same coin - that coin being fluffy versus crunchy.
Crunchy stuff can be used by both players and DMs, but fluffy stuff is almost exclusively used by DMs. And many DMs won't want the fluffy stuff since they may not play in that world. Kaptain Kantrip and I agree here (*gasp*). Hence, any solely fluffy thing is only going to reach 1/4 of the gaming sector - DMs who play in the world, which in reality, makes up less than 25% because the DM to player ratio is probably lower than that. I.e., more players than DMs, not at a ratio of 1:4.
Anyhoo, I'm rambling now.