Mass Effect ending question

[visualdeity]

OK, so I beat Mass Effect. It was great. What I want to know is... what did everyone find confusing about it? I recall people saying here that it was a real WTF ending, but it seemed very simple and straightforward to me. Did I miss something? Is the Renegade ending substantially different than the Paragon one? What's the deal here?

[Wangsandsuch]

I guess they didn't figure out it was leaving the series open for a sequel.

[battle_axe_of_doom]

^ if you wanna be specific they left it open for a trilogy with possible DLC expansions in between each sequel