Don't let the internet gossip turn you off. BRP has been in business for a long time and if there are problems I'm sure they can get them fixed. Heck, the company builds planes and trains.
I agree, overall the manual tranny is a solid unit, so you'll likely do fine.
I've managed internet community sites for over fifteen years, and the fact is a much higher percentage of folks with complaints post then those without complaints. When you think about it a bit, this makes sense.... just the way our society is. BRP is in this for the long haul, and if there is an issue, will bend over backwards. One thing you may want to check up on is how good a reputation your local dealer has.
As far as changing the oil, other than having to take of a few plastic pieces, it is no harder than any other bike, you can even use a motorcycle jack to lift it up.
Side note, the BRP that makes trains and jets is actually not the same BRP that makes recreational products (sea-doo, ski-doo, and can-am brands). They started out together, but are now entirely separate corporations.