pOOR Fella.. ok I try to answer you as much as I can. I own a Lowepro FastPack 250. I've traveled with the FastPack to Shanghai & Beijing (China) and Bangkok (Thailand) with it and I guess i'm sufficiently qualified to give you an user's field review. I have a 12" laptop which I slide at the back of the bag and the lower compartment houses my Nikon body, a fast 80-200mm zoom, a 18-70mm zoom and a SB-600 flash. Every year I would bring my bag to the local MotoGP at Sepang too, as well as a few weddings which I've covered so far.

Carrying comfort. Weight wise, it was bearable and comfortable when fully packed. the straps are generously wide to distribute the weight around. I have a Crumpler the Moderate Embarassment single strap laptop bag and is not as comfy as the Lowepro. However... something that you wont realise when trying it at the shop on only during field use you will realise it is that the belly strap can rub against your arms considerably when walking. At first you will notice it, but after a few good hours in the heat, the belly strap can get irritating and will cause chaffing on your arms and elbows. I'm not a fat guy either that my sides will protrude out but this is something that bothers me.

Heat wise.. hahaha.. it was summer in Shanghai and I remember sweating profusely. I guess this is relevant if you're planning to carry the stuff with the LowePro in tropical weather like Malaysia, the bag can get hot on your back. Within 10-15 mins of walking, the heat builds up and your t-shirt will be soaked with sweat. The design of the bag does not draw sweat away and it doesnt help being black colour too.

Function wise, my biggest No 1 gripe is that the 'fastpack' feature which is the zip doesnt open or close smoothly, especially when going round the corners. My bag almost always 80% of the time gets stuck at the corner and it takes some effort to pull it round to open the bag. I believe the defect is in the bag's design when there's weight in it, the shape of the bag gets distorted and some how folds the zip at an awkward angle.

Feature wise in terms of ability to carry & protect stuff, I'd say very good. Good padding all round especially at the key areas to protect your precious stuff inside. I've got it packed full of stuff before and threw the bag around a bit and still it was ok. Lots of nice large pockets and

Security. Could be better. Although there is a flap that locks down the zipped compartments, the zips are fastened with loops only. Places like Jahtujak Market (Thailand) will attract pick pockets and when you're busy shooting away with the bag on your back, it's common to find your zip opened by some fella. I need secure loops where I can slide a small travel padlock on. Steel loops would be better, but while the fabric string elastic loops will deter the petty thief, it wont be good enough to discourage a desperate thief.

wahh.. hands tired... hope this helps.