I'd love to try a 5-10 day trial before I plunk down cash on this. I was mildly impressed with Lineage II in beta, but as the people came forth and made the towns nearly impossible to walk through, I couldnt stand playing it.
From what I gathered from guildwars's site, you dont need to buy the expansion packs later on, you'll still be able to be just as "comptetitive" as the rest of the players, you just dont get to see the cool stuff.
Kinda like Planetside when Core Combat (yuk) came out. Heh, I remember, everyone was still up top with minimal crews underground getting the artifiacts that add bonus stuff.