I love the design of momentum itself, it’s a well done add. I really enjoy having such beautiful pictures in the background and it has such a clean look, which probably is the main factor for me to use this add on.
The only down side being that the add on doesn’t support Firefox iOS, please consider bringing this to Firefox iOS usages.

Eats 30% of CPU when opened tab left in incognito window (after selecting name and "work offline")

You need to add more languages.

Really cool extension, but I would like to have my personal start-page, and only use Momentum for new Tabs. If I can do this, then I'll give 5 stars.

Una pena que las opciones interesantes sean de pago. ¿Realmente alguien pagará por esto? Para mi gusto, faltaria poder customizar la hora de entrada y salida del trabajo (para el %). La barra de marcadores podría ser más bonita. Aunque realmente la extensión es muy buena.

Wow very nice extension with such serene and beautiful imagery but I wish I could have it only work for new tabs and not change my homepage. That's the only reason I had to uninstall. But after doing some tweaking to firefox I now have the best of both Worlds with my own homepages and Momentum New Tabs!