I can answer it quickly:
If you are looking for a strong
roleplay experience,
Yes. The only MMORPG I played for more than 1-3 weeks was Planeshift because of it.
Unlike WoW and other MMOPLGs(Massively Multiplayer Powerlevelling Games), there are lots of opportunities to roleplay and involve in several interesting events, guilds and such. However...
If you are looking for a strong gameplay experience, no. And this is valid for all mainstream MMO(RP?)Gs as well, in my opinion.
Killing thousands of rats/rogues/trepors... to score a level up, relying on pure luck to win a duel in PvP, swapping ores among containers to make stocks, pressing things repeatedly to craft weapons or remaining hours and hours pressing a shortcut to dig gold or another ore isn't what I would call a thrilling and fun experience, even though most MMOGs have the same "strong" gameplay basis as well, something I call:
treadmilling, as it's boring as hell for me.