I'm glad I did - it was a very satisfying project.
I had some oilskin/waxed cotton in my stash which I think might have come from fabric.com (that or eBay) and I ordered a kit that included Ann the leather for the straps, and the fastenings.
If you are a beginner the Merchant and Mills instructions are not as 'step-by-step' as some other patterns, but shouldn't be a problem for anyone with experience. I did make a couple of errors which involved trying to remove rivets (not easy and not fun) but that was my fault for rushing and thinking I knew what I was doing.
Other than that this was a really fun project. The fabric was a lot easier to sew than I thought it might be and I've learnt some new skills. In fact I loved the finished project so much I bought another kit from Fibresmith to make myself one to cart my marking to and from school.