I've done the trip several times but not in the last decade (although I don't think things have changed that much on VIA). Here are some random thoughts.

-I love taking the train. Everyone should do it once, if only to gain an appreciation of the size of the country.

-Don't be put off by the so-called dull parts. If the scenery doesn't catch your eye, use the time to meet people (train travellers tend to be very chatty and social... the "don't talk to me vibe" on a plane doesn't exist on trains), watch a movie, read, sleep, eat, etc.

-Do everything possible to get into the sleeping cars. Compromise on other parts of your trip if necessary. It's better to go in the coach than to not go at all, but having a bed, even just a semi-private berth, will make a huge difference in your trip comfort and experience. I tend to look at airline premium cabins as a bit of a fun frill, but on a long train trip sleeping accommodations are essential (unless you're under 22).

-Definitely stop over along the way. 5 stops may be too many for a 10-12 day trip considering the train doesn't run every day, but you should be able to squeeze in at least 3.

-The food is de-lish. Come hungry

Bon voyage, OP! Tell us about how your trip goes.