Not bad.  Certainly not as robust as the Microsoft desktop counterparts, but pretty awesome.  I’m now using Sheets to perform financial analysis and after some tinkering and digging today, I feel that I am a moderate level of comfort (which is about where I was with Excel).  For example, there are a ton of functions – I certainly do not know all of them:

List of Google Sheets functions

I also figured out how to reference data from another tab within the same sheet (similar to Excel):

Reference data from another tab