App switcher is acting more like app "restarter", especially when more apps are running concurrently. I assume this is due to current OS memory model limitations/constraints... Anyway, restarted apps loose focus (twitter, facebook, g+ apps will reload their content, loosing focus of currently shown content; pdfjsviever is restarted, effecively loosing currently open document).
The integrated browser is a story of its own - it will reload even the tabs, when swithing between them.
The above behaviour is a major problem for longer-term user experiece, since devices cannot be used for whole-day work, since apps are loosing focus on where the user left off in each app.
Please note that this behavior is visible on Ubuntu devices with 1GB and 2GB or RAM; and e.g. Android OS has no issues to do "real" applications switching (including multitab webbrowsing) while preserving contents of app on similar harware.
The webbrowser's management of tab memory was improved with ota 11, we are looking at other OOM settings.