Green Pepper rates this as "easy". This is not an easy pattern, unless you already have significant sewing experience.
First, there are details lacking in the instructions. In several sections the diagram referred to omits key details that are critical to someone new(er) to sewing (at whom I am assuming they aim this product). Of second concern is terminology introduced without explanation and techniques that are assumed but not described. If you've never eased in a curved seam to a straight one or sewn zippers, stand by. No mention of how to pin this or how to ensure a clean hem, just instructions to "pin and sew".
Lastly, Green Pepper's assistance line is open M-Th, 10-4 PDT. So, unless you're sewing this at work or are a professional tailor and doing this during the week, forget about getting any help.
The pattern itself is actually for a pack larger than you'd expect. This is a small hiking waist pack, not your typical-sized waist pack. Just an FYI.
Side note: Ripstop by the Roll's fabric is amazing, awesome and is the only reason I continue to want to sew. Green Pepper's patterns are maddening and I refuse to purchase another. However, RipstopBTR is an outstanding company with outstanding products.