Upgraded to Yosemite a few hours ago on my Macbook Air 11" and have had no problems at all. Homebrew works fine. My primary languages (Erlang & Elixir) run fine. Edited files with vim. But I've only done a fraction of my work for now (today).

Expect some sort of "visual overload"[1] once you upgrade. Too much of color (It felt like the interface was done with crayons). After a few minutes of work it'll feel normal.

The phone-calls-on-mac and turn-on-iOS-personal-hotspot-on-mac features will only be available in iOS 8.1, which is slated for an Oct-20th release. I am looking forward to these two features.

[1] - My friend called it that :)

If you use Asepsis then you'll get a message saying it's incompatible and won't be migrated, however if you reinstall it'll work just fine.