I don't think they'll have any need or plans to release a demo in the near-future. (Did they ever release a demo/free trial version of EQ?)
I'd say that if you have a strong PC with a good graphics card and 512M or 1G of memory, then if nothing else you could play the game to enjoy the visuals...it's great looking on 'medium' settings and absolutely gorgeous on 'high'.
I'm totally absorbed in it right now....even after having played some UO, EQ and many other MMORPGs in between then and now (including SWG), this is the first time I've felt a real 'newbie-rush' since those first two. They have more quests than you can shake a stick at, and while most are fairly typical 'fedex' or kill a certain amount of some critter, they are usually presented well, and there's enough variety to keep it fun. Grouping is lots of fun too, with monsters that are imaginatively designed and fast-paced action. I haven't done too much crafting yet, and while it sounds like there are still a few rough spots to be ironed out, it looks deep enough to be fun to do if that's something you want.
Overall, I think the game is a 'home run', and definitely encourage you to give it a shot.