Having completed the first two Mass Effect games, I can admit to being satisfied with the story so far. It's all a tad serious - there can never be enough camp in space operas - but well intentioned and I look forward to seeing the series close out next year.
My first Shepherd (male) was intended to be a downright space arsehole, and I deliberately chose the Renegade option whenever it was available. I didn't realise, at first, that playing good or bad didn't really alter things to much, apart from shop bonii and new dialogue options. It seemed to be just a matter of personal choice whether you played hero or arsehole.
In space, no one can hear you being a cunt, and no one really cares.
I'm not aware that being renegade Shepherd particularly changed the way the plot unfolded for me, and I was actually surprised when my Mass Effect 2 character import informed me that I had actually chosen the Paragon path by choosing to save the council at the denouement of the first game (although since I'm now playing for a second time with a decidedly angelic female Shepherd, we'll see what happens). I know that my conversation choices more commonly shifted to the less controversial as the storyline progressed, but I'm not sure if that's to do with my own personality, or if my Shepherd actually relaxed as time went on. I'd wanted him to be uptight and offensive to begin with, choosing a cruel visage when creating him, but he definitely mellowed. That said, it felt particularly out of character for me when he greet Garrus with open arms and a shit eating grin in ME2.
While male Shepherd was a ruthless spacer, the kind of guy who does what needs to be done and makes the sacrifices others can't handle to achieve the objective - none of the Normandy crew made it out of the Collector base alive, although only one of the squad died - female Shepherd is to be a career soldier, saved from the wreck of her colony and raised in the service. No nonsense, straight as a die and with little imagination; we'll see how long she lasts.