Ugh. I recently sold my Lowepro Slingshot 300 AW that I had for a few months. What a hassle that thing was. Sounded like a good idea: Swing it around to the front, grab your camera out and start shooting. It works fine for that. However, if you want to get any other gear out of the main compartment, you have to take it off unless you want to risk dumping your gear out on the ground, which defeats the purpose of getting a sling type bag. And it's a hassle to take on and off, especially if you wear a hat and/or glasses.
I would strongly recommend getting a shoulder bag of some type. I have an olive Domke F-4AF that I bought recently and I love it. It's tall enough to hold a D90 w/grip and attached 80-200 f/2.8 vertically on one side, plus my 85mm f/1.8, 50mm f/1.4, and my Sigma 18-50mm f/2.8 on the other. And that's just in the main compartment. There are four other large pockets and one small zipper pocket. My friend has a Domke F-3X ballistic that he loves. Crumpler makes good shoulder bags too.
The F-3X will easily hold what you have, except for the tripod.