At first, the o-ring was an issue for me, too. However, it was easily resolved by rubbing a bit of silicone grease on the o-ring. Now, my cup slides off and on very easily.
Thank you all so much for the information - I'm feeling very good about this! My husband will be makiing the stand for me so I won't have to worry about having enough room. I was definitely going to get the swabbie, but wasn't sure about the locker - I thought I might wait a bit for that piece. Then again, the skimmer will now be out of sight so it might be good to get.
the locker is AWESOME. you can get a version that connects to your Apex; and it will shut off when it's full and send you an email or text message letting you know it's full. I LOVE that feature about the locker. set it and forget it!