I have a Nature Trekker too and it probably get's about as much use as yours
, but does come in handy for storing all (or most
) of my gear.
I also have a
Lowepro Primus AW. Primarily bought as a travel pack, allowing me to carry a few other things in the top section along with DSLR and 2-3 lenses in the bottom. Love the side access and this was the primary reason for getting one, but be aware that, whilst the bag will take a camera with grip or one of the pro bodies, the side access is too small to get them in/out. I've since discovered it will take my D80 with Sigma 150-500mm attached, but only with a very tight squeeze and again not via the side access. Still it does the job and might be worth considering.