I like this solely for the video filters. Very nice for brightening up older videos. The pop out player is a nice touch as well.

Update after several months and I've come to realize I overlooked my favorite feature: forcing a specific video quality and not having to rely on YouTube's flaky auto setting.

One of the (if not the) best add-ons for Firefox. The only thing that's "missing" (that I'd love to have) would be the option of changing the aspect ratio of videos. There's a lot of stretched videos in 16:9 that were originally in 4:3 ratio. It'd be awesome to have an option to push them back to 4:3.

HIGHLY RECOMMENDED!
After a bit of frustration working out the best settings on how it customizes YouTube for me, I have to say this is the best add-on extension for Firefox I have ever used thus far. Truly an extension to be placed in the "essentials" category...a true gem! I highly recommend this extension to anyone looking to enhance the YouTube experience and provide a prime example of the capabilities of the Firefox internet browser. I will definitely be checking out any other works published from this developer and will be eager to sample anything he publishes as the quality and effectiveness of this extension is now my benchmark which I will compare the quality all other extensions too! I urge all creators to put the care, time and effort Maxime has put into this product as it would surly increase the overall experience of internet browsing and insure Firefox's place as the #1 most sought after, downloaded and used browser on the market today, which would translate to a higher market share for Mozilla, their partners and affiliates. Quality standards such as this would attract even the most skeptical and die hard loyalists who prefer other browsers. Elite creators like Maxime set a trend for overall higher standards and reliability of software products, further boosting confidence of having a more enjoyable overall experience. BRAVO, and well done Maxime RF! Thank you for creating this for Firefox it is truly a testament to your skills and I have enjoyed using your product immensely!

Brilliant, does exactly what I need

I have no idea why I haven't been using it since day one. Perfect solution, it only misses the display of used tags and other seo related things.