To understand the ambiance concept, you have to remember the Sailfish 1.0 version, before they broke some usability and consistency on the interface:
https://www.youtube.com/watch?v=ELMztxUHFjc or here : https://www.youtube.com/watch?v=y64ja7WBHU8

In those new days, the home screen had the ambiances on the left of the home screen, the events were accessible from anywhere with the bottom swipe, and the swipe down was meant to lock the device.

Then, the functionality is meant to replace the "profile" found in Symbian for example, not only to change the background color to match a back-cover.
For example, in my case I use 3 profiles: general (all ringtones at full-volume), work (call ringtone at low volume, no sound for mails/IM....), and silent (nothing except alarms), and like juiceme switch between them everyday.
The default ambiances are only there as a showcase, if you don't want to use them as wallpapers, but as profiles, you are meant to create those you need (and delete the default one if they get in your way).

If you don't need such granularity, then the "silent" pull down on the lock screen was the best option, but it disappeared. An option to reallow it would be useful.

Finally, there was a work in progress for a "situations" clone (in fact before situations was announced if I recall correctly) by SfietKonstantin : http://talk.maemo.org/showthread.php?t=93424 & https://github.com/SfietKonstantin/phonebot
I started to try to add a way to automatically change situations in response to time or antenna change events (to detect between home and work location without GPS) : https://github.com/Sagittarii/phoneb...872e7cd10b9ada
Feel free to take a look if you want to see the dbus calls to switch ambiences programmatically (like in a cron job).