It's not a big deal in any way, you get used to it and none of it breaks immersion. DirectX 9 has a few minor graphics glitches mostly related to drawing distant target circles, nearby AoE squares (such as a Lore Master's tar patches), and some shadows and lighting effects get cut off in odd ways when moving through some areas.
If your choice is between DirectX 9 and DirectX 10, I suggest you stick with DirectX 9. Once the game is installed and you've gotten it to run successfully at least one time, you can enable DirectX 10 if you want to. then you know that LOTRO runs great with Crossover and Big Sur. If you have time on your hands and read my entire thread about Crossover and Big Sur here. So just for fun I thought I'd try running LOTRO using DirectX 11.
