FWIW, I've never had a problem with my kindle, which has never been connected to the internet.
Even the 'special offers' dissipate after being in airplane mode for a certain length of time. I see no value in using any online feature—I've never taken my kindle off of airplane mode, and use Calibre to load all content.
I wouldn't have paid for the ad-free version of the kindle had I known it was just a lock-screen promo for a book. I'm exposed to so few new books in my life that I kinda like the feature. Then again, I also wouldn't have bought the ad-free version had I known I was going to keep it in airplane-mode since the day I bought it.
Back when I first bought my kindle and made this decision, I was thinking the ads would be something like a "checkout these deals on Bose speakers!" interstitials every three page turns.
Even the 'special offers' dissipate after being in airplane mode for a certain length of time. I see no value in using any online feature—I've never taken my kindle off of airplane mode, and use Calibre to load all content.