I know you said your interested in a backpack but Think Tank Photo just announced a shoulder bag that can hold a 70-200mm lens body combo and lots of other goodies.
It's called the Urban Disguise ® 70 Pro.

Thats why i said i was living at home at minimal expenses hehe.
Anyway, thinking it over, id actually recommend you get the Mp-1, like i said, you can always divide the big compartment, and this bag will last a long time so itll fit yer 600/4 aswell.
the zippers on this bag is serious heavy duty stuff.
i'm off ta bed,work early tommorrow, gotta earn more money to buy more stuff to lug around.

demi - I have a wife, so it will take me some more time than in Your case

Well, you can always add a divider to the main long compartment and have camera with lens + a lens there, so if you're planning on getting the 600/4 anyway, why not go for the MP-1, unless you intend to have several bags.
also the 200-400 fits nicely in there with camera attached.

took me a year to save up for the 600/4, and 2 yrs for the 600/4 + 200-400/4 + 200/2.
next lens ill be saving up for is proberly the 400/2.8, also id like the 45 pc-E, have the 24 pc-e.
but that was before the economic issues, and i had lots and lots of hours at work.
and i still live at home :D.

demi - thanks once again, I think I'll go for this bag, just need to decide which one I prefer, the MP-1 or MP-3, don't have the 600/4 yet, and it will take me a year or two to get it (hopefully, unless another economical breakdown will come, then I'm screwed), as for the extra dividers - have plenty of them from my other bags, so that's not a problem, padding also.

That's proberly because it doesent cost anything everytime you click, and you tend to like having the gear around you to make the shot.
So yeah, if i just go out birding i still have all my crap with me, which is why i bring the pelican case besides my mp-1 in my vehicle.

Sometimes i do however think bringing to much gear restricts us in some way in deciding what to use to make the shot, then again if you don't have the gear, it would suck when you get an idea and you're missing that fisheye lens or tilt/shift lens to make it happen.

many people seem to like overpadded bags, i don't.

Joe McNally,Laurie Excell among others also uses Moose's bag, and *cough* Thom Hogan *cough* also mentions the bag sorta warmly.

Again, id highly recommend it, if you pack your stuff right you're gunna get more worried about a sore back rather that if you can get all your stuff into the MP-1.

Most people tend to forget that carrying the bag on your hips is the way to do it.
Note that you can get extra padding for the carrying straps for more comfort on your shoulders, i don't know about you but i didn't get it, and ive found no need for it.
You can get extra dividers, i found i didn't need to.
another note is, this bag fully packed, you're proberly not going to be dragging it on a mountain hike unless you're superman.

thanks demi - I've seen the video, that's why I was wondering to move to this bag, I don't really care about the padding, as I've seen what a camera can stand (has some accidental drop tests in the past), or should I say, the weight is a bigger factor for me than the padding.

as for the amount of stuff, do You also has this idea, that after switching to digital the amount of stuff You take from one place to another has grown dramatically?

the MP-1 is my main bag, its served me well and as it states, all the flights ive had it on (which is about 10 trips back and forth so far) it fits in the overhead.
It has no padding, but ive actually done a drop test with the mp-1 and my Lowepro slingshot with a fragile glass in it, from half a metre hight,on concrete floor, the glass shattered in both the lowepro and the Mp-1, note that i did put the glass at the very bottom where it would hit first (im not talking glass as in lens, no worries) - i decided to test this cause moose claimed that at just a few feet it didn't matter if it was padded or not.

my OWN conclusion here of is that padding really ain't making it worth the size difference, and there is padded dividers in the Mp-1.

Have you checked out Moose's link where he shows how he packs his bag? i think you'd be surprised how much crap one can get into it. http://moosepeterson.com/blog/?p=6627
And yes, i have just about as much crap in mine as he does.
if you're looking for an overpadded bag, this is not it.

I would recommend the Mp-1, mp-3, mp-7 i have those.
The rest of my gear is in a pelican case, usualy if i bring a whole lot with me, ill use the pelican along with my mp-1 in my vehicle.
ive never shipped any of my gear, im not a pro so i don't bring that much gear with me on flight, if i did id bring the mp-1 and pelican case shipped.

BTW: I'm currently using Lowepro Rover AWII - it's very comfortable, but too small for my needs.

Yup, I'm talking about the Moose Peterson bag.

I've seen the Think Tank bags but don't have any experience with this brand, neither with Moose Peterson. So any feedback would be highly appreciated.

adamz said:
If so please shqre Your opinion.

You feeling alright there adam? lol

Are you talking about the Moose Peterson bag? What about the Thinktank bags?

Has any of You used thE WRP's MP-1 Photopack or WRP's MP-1 Photopack. If so, please share Your opinion about them. I'm looking for a carry-on size backpack, that I'll be able to take on board. It must have the size of a carry on luggage on one hand and be big enough to fit even large telephoto lens on the other. Any suggestions?