First do NOT buy anything without trying it on first and see how it wears against you. I'm serious. You're talking about something for hikes (like a messenger bag, day pack, sling). What feels good to me may be irritating as crap to you (or vice-versa). Go to someplace like a Best Buy or an actual camera store and try it on first.
Second, I highly recommend/second Dunfly' s suggestion of an insert. Here's why this is a good idea. A bag that screams "camera equipment" makes you more of a target for thieves than just a daypack (that every hiker or student has). Inserts avoid that problem. Inserts tend to be adjustable (so if you leave the 300mm at home but bring a speed light, you may want to change dividers). Third, if you already have a messenger bag or daypack that works for you, then adding the insert is the only change you need to make. I use an insert in a Lands End Messenger bag, and an insert in a full pack (more than a day pack). The only pure camera carrying setup I have is a Tamrac holster (when I want something smaller and lighter than my messenger bag. I do have an absolutely superb Thinktank shoulder bag but it almost never gets used--only when I'm bring multiple bodies and my 600mm zoom.
One other consideration--do you want it to hold a laptop or iPad? This is a factor in anything I buy because I sometimes will shoot tethered or will want to look at photos on a bigger screen.