It sounds stupid but one of the best features is the community. Ive never seen so little spamming, or abusing on realm chats that its actually good to chat with everyone as we're all friendly.
Graphics are good, the first 35-ish levels are hard but the Warzone will clear that up for you. And like Static said, the patches make Regnum better every month, but we still get a few bugs to Hotfix.
All in all, a great MMO, considering its free to play.