Most importantly, Sailfish offers real multi-tasking as we know it from desktop operating systems. While in Android or iOS your application is suspended when you switch to another one, in Sailfish they can run in the background.
That's not correct. Android has multi-processing. The Android runtime enables Service components to run in the background, and has preemptive thread scheduling, and has had these features throughout all publicly released versions of Android.
Sometimes I want to do something else while I wait for a large web page to load over my mobile data connection. On my n900 this worked fine, but as soon as I switch to another task, Chrome on Android 4.2.2 quits loading the page.
Plus, task switching is still a heavy operation on Android - swapping back and forth between two applications is a bulky, slow operation compared to the n900, which, itself, was bulky and slow compared to a desktop window manager.
The problem with battery life and multitasking on N900 is that it has so little RAM that it gets super swappy and starts to thrash esp. under heavy client-side js. I'm dying for an N900 w/2013 specs.
>Apple could give us "real multi-tasking" at the flick of a software switch
This is not true. Task management has to be designed into a multitasking OS. Maemo did a beautiful job.