Same for me. I fired up Firefox for the first time in years and it works great. The hardest part to get used to is their super-weird hamburger menu layout.
This menu is changing for Firefox 57. It will have a more "normal" menu soon. You can see it today by installing Nightly Firefox.
What Ankit The mobile menu? The mobile menu is a mess if you have extensions installed, because add-on developers don't put their stuff in the tools/page submenu, and there's no way to rearrange it.
Pressing Alt brings up the conventional menu bar, at least on Linux.
Plus you can go hamburger menu, customize, (some drop down menu at the bottom), show menu bar. First thing I do when I install FF on a new computer.