I had a Maine Coon when I was growing up.  He wasn't from a breeder, but
we were pretty sure he was near enough to 100%.  Still, he didn't have
papers or anything, so he may not have been precisely illustrative of the
breed. But he was a great cat, in all senses of the word -- terrific
personality and *big.*  He was affectionate and playful, energetic, and
could get pretty aggressive.  When he got that certain glimmer in his
eyes, my dad would get out the work gloves and really tangle with him.
The gloves were essential to prevent too much blood loss. :-)  He was
strong and liked to play rough, when it was appropriate.  But he was also
very good at picking up on when it was not appropriate.  His
aggressiveness was never a problem.  He was an indoor/outdoor cat, and I
don't know whether keeping him strictly as an indoor cat would have worked
out as well.  He liked to roam, a lot, and I'm sure he burned off a lot of
energy keeping the neighborhood critters in line.  (He certainly kept the
neighbor's half-Golden/half-mutt in line.)  He was definitely a scrapper
and would sometimes come home with the scratches to prove it, not to
mention other little surprises.  He brought home a bat once -- I
thought that was cool, but my mom wasn't thrilled.

We moved with him three times and he had no adjustment problems.  He
even seemed to enjoy the road trips when we moved from California to
Texas and back again two years later.  He had no attitude or behavioral
problems of any kind, and no health problems until he got diabetes.  He
only lived 12 years, which seemed like a long time to me (I was only six
when we got him) back then.

Sorry I can't offer more expert advice.  I'd check into how they do as
indoor cats if you are planning on keeping your cat indoors.  That would
be my only hesitation about getting a Maine Coon now, since I live in the
city.  My cat now (she's 15) is about 1/3 the size and doesn't even like
to venture into the apartment building's hallway. :-)