When I updated to WordPress 3.3, I noticed that - at least on my iPad - I couldn't see the buttons in the HTML view anymore. I deactivated all plugins and re-activated them one-by-one to find the plugin that is causing the issue and guess what, it was WP to Twitter. I have now all plugins activated besides WP to Twitter and the HTML view works like a charm. Once I activate WP to Twitter again, the buttons are gone and also I can't use most of the publishing options and can't add any tags.
As WP to Twitter is vital for me, I'd really appreciate if an update would fix this issue asap. Until then I'll have to deactivate it when writing and re-activate it when publishing.