Originally posted by jnorth
I love the Slingshot. At the time I reluctantly bought it because I thought I wanted the then not even announced 300. After more than a years use I know I don't. If I put enough of my camera gear in to fill a 300 it would be just to heavy to be comfortable for any length of time. As it is now I only load my 200 right up if I am going away or something and then pair it down for actually wandering around to shoot. The tot and snack thing leads me to the conclusion is that you will want backpack rather than a slingshot style.
In reality you will want several different bags. Just think of it as shoes or purses - you can't have just one pair of shoes or just one purse.
I have both the 200 and the 300. (My wife doesn't understand why I need both, but then I don't understand why she needs 3 dozen pairs of shoes). The 200 is fine for carrying a body with a lens mounted, and up to four rather small extra items (e.g., small Limited lenses). When you try to add larger lenses or flash units, it gets a bit cramped for my taste. It does have a separate compartment on top, but it is rather small. Plus the single shoulder strap is not the best for carrying a lot of weight. I usually carry in the 200 a K10D with DA 12-24, a DFA 50mm Macro, and either a FA 77 Limited or an FA 135mm f2.8 (or sometimes both).
The 300 is much larger, with 6 compartments for extras, each of which is larger than the 200's compartments. The separate non-camera compartment is also much larger. Plus, it has a padded hip belt like a real backpack to transfer the weight to your hips. It would be a good choice for the O.P., with plenty of room for all current and future gear and lots of room from snacks and water (in a completely separate section). You do need to unstrap the hip belt to sling the bag around, but it is certainly more convenient than a backpack. I use mine when I want to carry my Sigma 100-300mm f4 EX DG which is 8 inches long and over 3 lbs, so it doesn't fit in the 200.
Of course, for a lot of weight and/or a lot of walking/hiking, there is no substitute for a real backpack. I use a regular hiking backpack from REI with Domke inserts for photo gear. I prefer a regular backpack over the dedicated camera backpacks, but I don't carry a ton of gear on long outings.