I've thought about a pack cover for rain but decided against it (may change my tune later). Instead I put my water protection INSIDE the pack. I don't care about the pack per se getting wet as long as my sleeping bag and clothing stay dry. I've used plastic garbage bags as pack liners but lately I've been trying splitting my stuff into two or three drybags that I put inside my pack. That helps keep things organized and dry.

If the pack gets wet while I'm hiking then it's as wet as I am so I don't notice. But a completely wet pack is a bummer to put on in the morning in your dry clothes because the shoulder straps and belt make you wet. Sometimes I carry a garbage bag that I put my pack into at night to keep it dry in case it rains while I'm asleep. But when I'm hammocking I use a biner to hang the pack from my hammock supports so it stays as dry as I do.

I'm currently experimenting with a new strategy. Rather than a rain jacket I'm trying a poncho tarp that is big enough to go over the pack. I'm going to see if I can use that in place of a rain jacket,pack cover,and tarp. It would certainly lighten the load but I'm used to an 8x10 tarp so I may find that this doesn't provide enough shelter. We'll see.