I always use both panniers although only one is full of commuting stuff, I like the ability to stop and get groceries on the way home if needed.

Happy biking

...another vote for panniers.

I don't have any on my bike at the moment, but since I started driving to work on Monday's with a week's supply of clothing and food, the rest of the week without a pack on my back has been much better. I don't mind the weight on the bike, but like others have said, having the pack on my back makes it sweatier. I don't like that.

As soon as I can get them on the bike though, they'll be there so I can avoid driving whenever possible.

Sort of. I have a collapsible side basket that I drop my work backpack into. I really don't want that on my back while riding. I can also fit a bag of groceries in there (not at the same time). I also have a trunk box on top of the rack that hold tools, spare tube, etc, and could hold my lunch if needed. I'm thinking of adding a second basket.

I use a messenger bag from tom bihn for my laptop, and I have a rockin pair of black wald foldable metal grocery panniers which are bolted onto the bike and get used for farmet market runs or anything else I need.

Panniers, simply because I sweat enough with the 80-90 degree heat and 80-90% humidity that is South Mississippi. ;)

I'd rather carry the extra weight with my legs, then on my back...panniers.

don't like the feeling of the weight on the bike. Everyday I have to carry my laptop, clothes, and lunch but I've gotten used to the backpack and don't mind the sweat to much. I'm looking into getting a Chrome Messenger Pack because it'd work a little better than the backpack I use now, and it'd be waterproof.

Carrying a back pack makes me appreciate the weekend leisure rides more, also I'm pretty fast without 10lbs with me.

Yep. I use one of the trunk/pannier combos. It's perfect for what I carry.

I use a backpack, but I don't carry much (usually I don't carry anything), and my commute is only 1 mile