Yes appium is very good tool for hybrid apps,webapps,native apps.
It will work with MAC OS/ Windows both
If u have only mac machine then you can automate both android and iOS app using single machine
for android app u can download android sdk bundle for mac machine and create avd and run u r scripts
for ios app also same android sdk bundle will work with simulator
If u have windows machine then u can only automate android app this is limitation of windows machine and not appium becoz we cannot run simulator on windows machine, but we can run emulator on mac machine...