So far I have used Google Drive to share spreadsheets for planning with colleagues; collected marks and assessment feedback into a spreadsheet; set up numerous surveys for staff or students; created quizes for students and written and shared various working documents.
I find it for the most part extremely user friendly. The ability to run surveys easily and collate the results is very useful. I have used it throughout this year to gain feedback from students about how particular units were run and to see what they thought I could improve.
I have tried running Flubaroo on multiple choice test results and was able to grade the test without having to mark every single paper, which was a pleasant time saver.
I think the biggest benefit comes from having instant collaboration with colleagues. I look forward to further development from Google!