Recent postings have speculated on the 2009 changes to the GoLite Jam2. Based on a side-by-side comparison of a new 2009 Jam2 to the original Jam2, the changes include:
-- Added spacer mesh to the back panel.
-- Added mesh to the waist belt fins (providing slight padding).
-- Added zippered mesh waist belt pockets with internal organizers (small flat pockets-inside-the-pockets, approx. 3"x4", presumably for keys, lighter, etc.).
-- Replaced the compactor hooks on the bottom of the pack with a larger style(the same as those used for the ice axe retention loops).
-- Side compression straps can now be streteched across the back and joined to the opposite side, as on the Venture series.
-- Replaced the compression strap buckles with a different type (which seem to provide easier adjustments).
-- Replaced the waterproof zipper on the back pocket with a regular zipper covered by a flap.
-- Changed the type of mesh used for the internal hydration sleeve.
-- Changed the pack bag fabric. (A GoLite representative told me the fabric has not changed but it clearly has. The new fabric seems to be what MLD calls "Dyneema X," with an additional nylon X pattern overweave at 45 degrees to the Dyneema grid.)
-- Added a built-in whistle to the sternum strap buckle.
-- Enlarged the haul loop.
-- The back vertical seams are no longer flat felled (single row of stiching instead of two).
-- Side pocket construction (the way they are sewn to the main bag) has been modified and the elastic used on the top of the pockets is stretchier.
-- The attachment points of the ice axe loops and bottom compactor buckle loops have been reinforced.
The dimensions seem to be unchanged. The weight has increased approx. 7 oz, from 20 oz to 27 oz (men's large, measured on my scale, rounded to the nearest ounce).
My comparison was based on the original Jam2, purchased in Jan-07. I do not know if any changes were introduced in 2008 but GoLite confirmed the major 2009 differences -- back and waist belt mesh, waist belt pockets, compactor improvements, and back pocket zipper.
Pros (imho): Waist belt pockets (!), back and waist belt mesh, improved compactor system. The "Dyneema X" supposedly improves abrasion and tear resistance but I have been satisfied with the performance of regular Dyneema.
Cons: Significantly heavier. Vertical seams appear to be weaker.