Re: LotRO DX10 Client = BOING!!1!11!!
If you're playing on US servers, I believe Brandywine has the highest population. Elendilmir has the largest PvMP community as far as I know. So if you want to do some PvMP I would recommend starting on Elendilmir.
DX10 performance is okay, but isn't as good pre-book 13. There will be a large update starting from your DVDs. I recommend doing something else for a bit when updating.