While either way, I think the first time I didn't get it to seal or open properly since about an hour later while I was on the Skytrain to school and I felt something go THWACK and I jumped a little bit in my seat, garnering a couple stares. @_@ It didn't hurt but it's not something I'm used to. It's day three and I think I'm getting the hang of getting it in properly. Thankfully the people on the train are used to sleep deprieved students so weird behaviour can be passed onto other reasons.
No leaks so far, but I am having trouble getting it out. I think it's the suction. I'm unable to get my finger of the rim and even bearing down I have trouble grabbing and sucessfully pinching the bottom the bottom. Either way I'm loving my cup so far, it's definitely a keeper.