I actually have an account I used to use speciffically for getting people into the game, unfortuanetly I've been using it to gvg recently, but send me a pm and I'll see if theres somethign you can use. If you do decide to buy the game, I highly recomend you do your research in which campiang to buy, (unless you get the trilogy).
www.guildwarsguru.com is a good place to start.
To answer your orginal quest about whats absolutely awesome about this game, I'd have to say the complete reliance on teamwork. in any end game areas, or in pvp communication is the absolute most important part of gameplay due to the weakness of indivudual characters. Skills are balanced with the assumption that combinations are availiable to the team, not indivudually.
Outside of those areas, I guess my personal favorite part is making new builds. uit takes a long time to gain an understanding of what is necessary in team builds, but once you have that down theres ome really fun combinations to explore. Of course I do
extremely unconventional stuff in random arenas, and it some times annoys my teammates even when it works.
Endgame pve is a bit different than other main stream MMO's due to the relitive lack of a tanking position. There are areas that use tanks, but most of the game can be played with a good amount of defense an a large amount of pressure. at the same time this makes backline positions even more difficult.
The one last thing that I would have to say stands out in GW is the extreme diffiiculty of the end game pvp. guild versus guild requires to to have only 8 people cover three or even four objectives, and often results in 5v3's or other unbalanced positions, requiring a large amount of skill in knowing whether to engage delay or just hightail it out of there. Even in the most unbalanced metagames there are a large variety of viable team builds and strageties that come into play.
For HA, the difficulty is also high for very different reasons. Most of the combat is 8v8 or 8v8v8 with a variety of match types. this means that "spike builds" (builds that can kill enemy players in a fraction of a second unless an enemy monk catches the "spike" at common. Adaptability is traded for extreme damage and defense in hopes of taking over specific points on the map.
as usual my post ended up three times as long as I meant it to. Anyways, contact me if you want to try the game on that account. Its semi-pvp ready, and I could probably get you into a game or two with my guild.