Commuting Rucksack Recommendations Please

Deuter Trans-Alpine.
http://www.chainreactioncycles.com/Models.aspx?ModelID=18436&PartnerID=2...$ja=tsid:41244|cgn:awin|kw:78888&awc=2698_1365334924_84429e71a7e9aa95ff0096a4abcc154c

Super comfy, loads of pockets, light, waterproof reflective cover. Very very good.

I'd also happily recommend Osprey. I have an Escapist 25 (http://www.ospreypacks.com/en/product/multi-use/escapist_20) which is still looking great after 2 years of use.

Very handy lid lock to carry your helmet, light loop to hang a rear light from, reflective panels, plus a very useful rain cover. I can carry a 15" MacBook Pro in it without a problem. Little pockets on the belt, plus one on strap. Also use it for day hiking.

I spent absolutely ages looking before I chose, as I wanted all of the above. I ride in Rome, and yes, your back will get hot, but not overly so.

Vaude make good bags for cycling, I used one for years before I converted to a rack and pannier. You get much less sweaty, take the load off your back and can fit more things in the panniers than in a back pack should you ever need to. I made the change four years ago and have never looked back.

I also have an Osprey Momentum 35 and would happily recommend it. Was a little concerned about it's durability; after a week a small hole had formed in one of the front pockets where a pen had been rubbing against the inside. I moved the pen to a different location and in the subsequent year have had no further issues and it still looks pretty new despite daily use.
I'd previously been using a Berghaus hiking rucksack, which was pretty good but the various little touches rodsquad mentioned make a difference and make it a better choice, in my opinion, for commuting.

I would also highly recommended Osprey. I have a Momentum 35 lt and it really is a great cycle-specific backpack. Got an expandable main compartment, external pockets for easy access. and a stuff away waterproof cover. I carry wash kit, towel, complete change of clothes, shoes, waterproofs, and tools. So I needed a big bag. Its not cheap and its not minimalist but it is comfortable, massively adjustable and tough. It has great little touchas like mini pockets on the straps. One even has a retractable lanyard. I hold my keys and work id card in them which is so useful. It has little loop to hold your helmet off the bike and front pocket designed to hold a D lock. Lots of great ideas which add up to a useful commute bag. On the subject of sweat. If your wearing a rucksack whilst cycling. You're going to get a hot back.

Not sure what brands may have the style over there, but a great American design is a backpack/messenger bag monosling. The weight is against your chest rather than on shoulders (and therefore lower back). I use the north face striker.

I really really like my Ortlieb Velocity - I've had mine for years. It is very comfortable, and there's chunky foam with large gaps in between to keep it off your back.

That said, the times that I have to carry the laptop every day - after a few days I stick on the rack & pannier. It's just less pressure my back for the commute (20 miles each way). If the commute was half the distance I'd probably stick with the velocity, its so much nicer having the bike free to move when you stand up.

I stick the laptop in it with a neoprene slipcase. It's waterproof, and the yellow adds a bit of visibility, but it isn't hi-viz. If you want that just put some hi-viz stickers on it.

edited to add: I mostly rode with a 13" Macbook Pro (2008) - 4.5lb (2.04kg). At the moment due to ****ing job I'm using it every day (but not cycling) with a 15" retina MBP - also 4.5lb. Both fit fine, but note both are fairly light laptops. You don't want a heavy laptop on your back.

Any ventilated back rucksac curves which makes being laptop compaticble a nightmare.

I have always got on with osprey packs i think this one is new , it has a enclosed ventlated back from the looks of, but i have always found osprey packs to be less curved than others.

http://www.ospreypacks.com/en/product/multi-use/syncro_20?tab=features

good luck with the hunt

I've got a hiking bag, and use a hi vis cover for the dark and when it's wet. Does the job well. It's got a light metal frame and a mesh back to vent the thing and keep sweat from getting trapped.