Rated 4 out of 5 stars
I didn't need the calendar bit that comes with this (because I never use it anyway), but it's easy to hide.
The important thing is that Gmail contacts are back where they belong - INSIDE gmail instead of stupidly and idiotically opening in a separate tab/window.
Now, if the creators of this can just give us the 'old compose' functionality (because the Old Compose addon hasn't been updated in 2 or 3 years), then I'll really be over the moon and would give this a 5 star rating instead of just 4.
I don't like fussy, time-wasting, complicated and ugly - and I don't want much, but out of the 2 things I most wanted restored to Gmail, this addon has provided one of them, so thank you.