I voted No in the poll, but only because of the backpack - my back sweats horribly, and I also feel unbalanced if I have any weight in one. I've always used a rack and whatever attached bags are appropriate - panniers, top bag, or both. In my uni days my bag was usually a plastic carrier bag secured with bungees. But the distance should be fine.
On the security front, my bike looked ratty, because it was obviously old and with a deteriorating paint job - and usually dirty, because I rarely cleaned it except for the chain. But it was actually quite a nice Ernie Clements Falcon, and it's the bike that even to this day I've probably covered the most miles on. It's definitely possible to get a decent bike that looks like a pile of junk.
I used to lock it in the uni bike racks with a reasonably thick cable lock - obviously fairly easy to cut, but the cable was thicker than most in the same rack, and the bike looked a lot less valuable than most. My theory was that a thief would want to be quick and would go for the most obvious combination of nice bike and weak lock.
And I think it paid off. One evening a friend and I cycled into uni for an event, and we locked our bikes next to each other to railings outside the venue, with similar locks. His was an almost brand new bike which looked flash, though mine was actually a better bike underneath. When we came out, his cut lock was on the ground and his bike was gone, while mine was still there. Thankfully he was insured and they paid out. We mused at the time that we should have put each lock through both bikes, but I guess it's possible that might have led the thief to cut both and take both bikes - hard to say really.
Another friend at the time had the theory that buying super cheap rat bikes and not even locking them up was the way to go - and to be fair to him, they looked like bikes that you'd throw in to the canal rather than trying to rescue, and each one probably cost less than a lock. But by the time we parted at the end of our courses, he'd had about 6 or 7 bikes stolen - I suspect by drunks looking to get home.
