I was a very early adopter when Ron first announced the Burn. I had been looking for a smaller volume pack for some time now as most of my trips are 3-day or less. I basically ordered mine the first day he had them listed and recieved it that week (happened to have a few in stock).
Overall, the pack has been great. I'd agree with someone above who stated one's gear list needs to be well sorted. The pack is slim and minimalistic. I found the large size perfect for my 6'3" frame. Load carrying is solid and 20lbs should be zero issue.
Breaking the pack down further, the pack is made with dyneema gridstop. Those familiar with ULA packs will be happy to know, this is the same material. Tough as nails, seems to handles some level of rain/snow pretty well and wears like iron. It's impressive such a "heavy" material can still produce such a light pack.
Layout wise, the front panel mesh is a heavier version (again, similar to what ULA was using). It's a nice expandable pocket that can handle a lot of gear and due to the packs profile, I never find issue with snags or getting hung up. We were in the White's this winter right after they picked up like 60" of snow over 3 days and there must have been 20-30 blow downs of various density and I just plowed through them without issue. Pack is seriously tough.
Ron has integrated a nice closure strap from the top of the pack to the top of the mesh pocket. I would have prefered if the anchor point on the back panel of the pack (between the shoulder straps) was possibly sewn to a larger section of webbing to better distribute the pressure that strap places on the pack when cinched. Right now it's a .5" piece of webbing just anchored into the seam where the extension collar is sewn into the body. When tight it places a fair amount of pressure on that point. I'm really nit picking here but figured I'd point it out. Std draw cord closure for the top of the bag.
The Burn uses nice heavy (higher tension) bungi cord that actually does it's job and holds things solid. I used the supplied bungi to make a criss/cross compression matrix across the mesh front panel as well as a triangle compression cordage similar to what's shown on MLD's site for side compression. This allows some load control keeping everything tight.
Shoulder straps are nice items. Fairly thick padding but the straps themselves are pretty narrow. That being said, I haven't found any issue with them digging in during use. Ron intergrated nice finger loops on the end of the shoulder adjustment strap which aids in adjustment as well as providing a nice place to allow one to rest their arms/hands during hiking.
Waist belt is a simple 1" webbing attached to non-padded wings. I was concerned this would be semi problematic depending on load weight but at least thus far, hasn't proven to be an issue. If your a cincher, I'd probably recommend adding a little ccf padding there. I still might do it myself but as mentioned, haven't had any issues thus far but that's during winter months were your clothing provides some level of padding. Time will tell.
Pack volume is pretty small. As mentioned, you need to have your gear list well sorted. To answer the previous posters question, for winter use I load my stuffed WM Versalite vertically in the bottom and then stuff my cuben duo right along side. Perfect fit and utilizes pack space nicely. I think/thought I tried stuffing the Versalite horizontally along the bottom of the pack and if memory serves me right, it was a real tight fit and pulled the pack out of shape some.
So packing wise, I fold my neoair into thirds and lay that in on the back panel, then goes the Versalite and duomid into the bottom. Next goes sleep clothing/spare draws/socks, then food generally, then common use stuff up top. Depending on time of year this can range from an outer shell, down jacket, fleece, gloves, microspikes, hat, wicking shirt, etc. From there I put my medic kit, toiletries, tent stakes/gc, alchy stove into the front mesh pocket. If I'm pulling gloves on/off or a hat or shell, I'll also stuff that into the mesh for easy access. Water in the side mesh pocket (sometimes alcky stove) and I'm ready to roll. I've also added straps for carrying snowshoes as well as used the bungi to lash supplemental ccf sleeping pads to the bottom of the pack.
For summer use with a quilt and tarp, my load volume goes down even more and space opens up nicely.
Overall a great pack. I'm sure given some careful planning and pairing of gear based on condtions, one could get 5-days from this pack.