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As Roland mentioned, the Pelican's weight will be an issue for non-USA flights where the airline controls weight. If you fly international direct to destination on a US carrier, it won't be an issue as most allow 40-45lbs for carry-on and rarely ever weigh anything at the gate. The Pelican 1510's size is not a problem either. It obviously fits large planes, but also 737s, Airbus 319/320, the Embraer E series, some of the regional jets, and even in the latest version of the Bombardier Dash 8 Q400 turboprop used by United/Continental.
Rollers are great if you're traveling mostly in modern urban environments with smooth walkways, but are not ideal once you're away from paved surfaces, unless you need it for storage in your own or rental vehicle. The benefit of a Pelican over a TT or Lowepro roller is that it can be put in the luggage hold with less risk to the equipment. It's not that you want to always do this, rather, there may be times when flight crew tell you it's the only way you're getting on the plane. If you go for a soft sided roller, make sure it can fit completely under the seat in front of you without sticking out into the row. If you have to sit with your feet on the roller, then it's too long and the cabin crew aren't supposed to allow this, especially if you're not at a window because it will hinder other passengers in an emergency. Sometimes you can turn the roller 90 degrees, but then you'll encroach on your neighbour's space and some under-seat areas can't accommodate this. Another challenge with under seat storage is the number of different types of in-flight entertainment systems that have space hogging equipment boxes under the seats.
And what I think is just as important as the type of bag you travel with, is the strategy you use to get the seat you want, and if possible, related boarding priority to ensure you have sufficient storage options available. I would highly recommend using the website seatguru.com whenever you're researching flight options to determine if the available seats for a given flight provide what you want, such as seat pitch, power outlet, whether equipment boxes encroach in the footspace area, etc. Also know your airline's boarding procedure. For example, many board from the back to the front. But some like Southwest and US Air base boarding priority on other factors such as whether or not you used online check-in (you should) and how early you did so (the earlier the better). The benefit of a seat at the front is that you will deplane faster if you have a tight connection or that you're in front of the engines where it's less noisy, or away from the lavatory where there might be more foot traffic and unpleasant odours. But the tradeoff will be that unless you have elite status with that airline, you will be among the last to board. And what is increasingly the case now, especially in the US due to checked baggage fees, is that everyone carries on as much as possible. So if you're last or late boarding, you could be SOL. This is especially true for the second or later leg of a tight connection. The last few flights I've taken the gate agents have announced that passengers in the last couple boarding zones are not guaranteed any overhead storage space and will be required to gate-check their bags if none is available. The only space you're guaranteed to have is that under the seat in front of you. If you can pack for that space, you have less to worry about. Otherwise, try to have a seating and boarding strategy.
For my needs, I use the Pelican 1510 with dividers for most US domestic travel. When I travel internationally, I usually fly with a medium size backpack and a 'laptop' bag that contains a MacBook Air, which takes very little space, as well as more camera equipment in that bag. Currently this combo has been a repurposed Arcteryx Blade series backpack (I use the now discontinued Blade 21) with Domke inserts, and a TT Urban Disguise 35 for the laptop and more gear, though sometimes I'll use a Domke satchel instead. If you can avoid over-padded bags, then you will be able to fit more gear in a smaller space, but this seems to be a mental block for most who seem to prefer traditional camera bags. In this respect, the Gura Gear bags appear to be excellent (I have not used one).
In case you're curious, this is the DLSR kit I fit in the Arcteryx bag:
Coincidentally, it's quite similar to what will fit in the Pelican 1510. There are photos and more of my thoughts in a blog post I did a little while ago.
I have recently reconfigured the kit I use to reduce size, weight and improve certain image quality aspects. Of course this suits my needs and will likely differ from yours. It has become a two-brand system split between the Leica M series for all wide angle and most normal focal length applications and Canon for telephoto and some technical uses, such as tilt/shift. My gear set, as pictured above, has been reduced from two huge DSLRs to one with two zooms (16-35 & 70-200, with the 16-35 brought primarily as a back-up to the Leica) and one M9 body with 12, 21, 35, 50 and 90mm lenses. Those lenses and the M9 fit in a Domke F-5XB size bag, which can also carry just a 70-200 f/2.8, to give you a feel for the real space savings that can be gained from a more compact system.
Oh, and one last tip. If possible, ditch Canon's rigid plastic lens hoods for a decent collapsible rubber one that can be used on multiple lenses with step rings. The rigid hoods add to the diameter of each lens, consuming precious space.