5lb seems quite reasonable for a 65 litre framed pack, though it is possible to do better with specialist lightweight packs such as the Osprey Exos 58. To get better weight savings consider whether you can reduce the size. It depends on what you are doing with your pack - if you are just doing 1 or 2 night trips in warmer seasons then 40 to 50 litres could be enough. And if you lighten up then maybe you wont even need a frame. This will give you many more options for lightweight packs - The OMM villain and Golite Jam (2) spring to mind.
Until recently I alway took a 70l pack (Osprey Aether 70 - highly recommended if it fits your requirements) but I realised that I rarely use all of the stuff I cart around in it. Especially in summer its too much volume, which I tend to fill with non essentials. As an experiment I dumped everything except the stuff I used on my last (3 day 2 nights at bothies) hiking trip (and kept the safety gear etc) and I found that I could easily fit everything in a 35l dry sack, including a ccf sleeping mat. This didn't include food and water or shelter, but there was more space left in the dry sack and overall I reckon a summer weekender could easily be done with a 40 to 45 litre pack - certainly my trusty aether 70 will be staying home on my next trip.
Dont forget to try on any pack with a dummy load before you buy - this goes double for lightweight packs as often part of the weight saving is achieved by get rid of adjustment mechanisms.
We agree with otaku-steve that around 5lb wouldn't be over-heavy for a decent 65L pack. If you lose more weight on the pack itself, you are probably losing comfort and features. The Deuter packs we stock are over 3kg - but they have superb back systems and lots of features, whereas the The North Face Terra 65-RC is 2140g with fewer features (it doesn't cost the earth either). It's a trade off: comfort and features against weight, and as suggested above, getting the gear weight down is probably the best route depending on your trip. Have fun!
Certainly not an insane weight, although you can certainly drop some weight without losing anything much important - here or here say.
Thing is though that if you are properly filling a 60+ litre pack it'll be a lot of weight and so the rucksack really will have to fit you very well and the extra 0.5kg (or even 1) or so isn't such a massive percentage gain weightwise.
So if you're into a program of weight loss from everything, start by trimming everything else down then see what sort of smaller rucksack it fits into.
Less weight and less volume means you can go for a smaller, lighter pack, and a more enjoyable romp in the outdoors.
Cicerone have signed me up to give a Lightweight Trekking talk at ExCel on January 12th, from 1630 to 1730. I guess I'll be doing my usual thing of staggering onto the stage carrying more lightweight kit than I can comfortably carry!
