We did it last july - PR to Hardy.
Spectacular scenery, but spendy - we were on motorbikes and IIRC, it was still over $350.
Was on the Northern something (Expedition, Adventure, Queen of Much Needed Repair, can't remember which) early morning (5am told to be in line, 7am departure) and you don't get into Hardy until just after 11pm.
On that boat there was big comfy seats with floor to ceiling windows - the cabins seemed to only have one small window, so based on that alone, I wouldn't bother with the cabin.
Basic ferry food, but they did have a BBq on the back deck for lunch as well as a couple extras for dinner.
Travelling down Grenville channel you are almost literally meters from the beach.
However, we (and seemed like everyone else as well) reached a bit of a breaking point ~8pm - by then it was dark, you'd been on the boat for a long time, and it was time for it to be over, so arrival in Hardy was a bit of a relief. You get in late so unless you can sleep in the truck, a hotel that night is necessary.
We had good weather as well, only a bit of swell when you reached the open ocean, so no issues there.