Are there any seasons that jump the shark and are tough to get through?
Now that the show is not airing anymore, and you can rifle through episodes and seasons pretty fast/easily, it doesn't really drag. There were some spots that did drag on back when it was airing because of the writers' strike, but I found upon rewatching the series that when you're moving through the show at a good pace it doesn't really drag like it seemed to back then. So you'll be fine.
Just know that there will be some parts of the show (episodes or storylines) that don't really affect things (like the overall plot) too much (that was a big gripe about season 6) and you should be fine and just enjoy the ride...and it's a hell of a ride, and I'd easily recommend the series to anyone who hasn't seen it.
As for the ending...like you said, some loved it and some hated it. I, for one, loved it and thought it was great. I hope you do as well.
One of the most enthralling shows I've ever been a part of, and I am glad I was able to watch it as it aired, from pilot to finale. That being said though, I'm jealous that you're getting to experience it for the first time.
This post was edited on 3/12 at 8:44 am