Well worth it - Eberlestock G-Series Featherweight Rain Cover

Big fan of the company, fmr Marine I can tell a quality product that will last. Keeping your gear dry and fresh is a top priority, this makes it easy to do so. It will work on most any large pack frame but the Packs Eberle makes are top notch (I have Gunsliger II).
I live on the gulf and it rains pretty much daily, after about 20 rain storms and daily highs of 100ish its holding up like new.
Pros: ease of use, cost, quality material
Cons: N/K

This review was written in the old system and had content requirements that are different than reviews written today.