Today I just felt too crappy to ride the bike to work, so I took the train/subway. Gave me the option to stuff even more in my backpack than I usually do and bring loads and loads of clothing to work. So I'm set for the upcoming two weeks and basically don't need to bring a backpack with me anymore for now.
I took my lock with me as well, will be locking it to the bike shed during lunch break, which saves me even more weight.
Tomorrow I'll try to ride packless and see how that works out.