I like all of it, but most especially their free-to-play game Sansar is amazing! The best part about SL for me has been being able to meet people from across the world who share my passion for this wonderful place we call Second Life. It's also great having so many different options in how you can connect with others here as well - whether by chatting or doing things together such as building houses/landscapes etc.
There are some features which have not yet reached full maturity (such as using