Amazing Rated 5 out of 5 stars
I've noticed that I could not live without the threaded view after using Gmail Web for so long, and this add-on does exactly that and it does it perfectly. It's incredibly efficient and I've never saw a missing message from a thread.
The only thing I'm not very comfortable with at the moment, is that it requires the options "Global search and indexer" and "Inbox and sent synchronized for offline storage". I make intensive use of Thunderbird (always open) and have an SSD as my primary drive and those options cause constant writing to the disk, which is not very healthy for an SSD.