I began using Firefox a long time ago (when it was called Phoenix) but switched to Chrome.

A couple months ago I switched back to Firefox because Chrome lost my open tab session in some cases (hard crashes when loading the old session), due to privacy issues and because it often triggered long swaps (locking the process) when dealing with lots of tabs (I usually have like 50-60 tabs open in several windows). Also because I support Mozilla's values.

Unfortunately I'm not very happy either. Alongside the issues commented here, I noticed these problems:

- Sometimes it just goes to 25% CPU usage and the browser becomes really slow. The only choice is to close all windows and open Firefox again.

- Multimonitor and Flash sucks. I'm not sure if this is Firefox or Flash's fault, but it often chooses one window as its parent, regardless of where the tab with the Flash content is located. Clicking/hovering the embedded object fails when the object thinks I'm in the wrong monitor. Also, going fullscreen usually pops the window in the wrong monitor.

- The JS PDF viewer is slow as hell (I once spent 5 minutes waiting for it to zoom, and I couldn't close it because I feared losing some changes in other tab). Firefox's JS engine is quite slow in and of itself, who thought it would be a good idea to embed a JS PDF viewer?

- Extensions take ages to be updated in the Addons repository (especially compared to Chrome) which frustrates extension developers and users. I personally know a developer who had to move away from it and tell users to update the extensions themselves.

- When a JS script is locked, the whole browser locks.

- If you close a window by mistake, there's no way to bring it back, so say bye to your precious browsing experience. "Undo last tab close" only works in tabs within that window! So frustrating. EDIT: apparently this is possible, check https://news.ycombinator.com/item?id=5905649.

- The latest contributions seem to focus on how to be more like Chrome, and less about providing users a better product[^1].

- Did you ever need to mess with about:config? Black magic.

- Tab groups suck. They're useless and there's no way to disable them once you activate it by mistake. You have to mess up with about:config (see above). Talk about a great UI.

They completely lost the track on what users need. We don't need another Chrome clone nor cool UI changes in each new version (especially when they get them so wrong). They probably spend lots of hours tweaking things that didn't need tweaking. What's wrong with the current UI that needed such a big overhaul? We need a browser that works, not one that looks like Chrome.

Mozilla, making Firefox look like Chrome won't make users switch back from Chrome. If people want Chrome, they'll stay in Chrome. Period. Get rid of termites before painting the house.

[^1] E.g. http://limi.net/checkboxes-that-kill or the new UI which is a ripoff of Chrome's. I can see his point about the "checkboxes kill", but removing features with perfectly fine use-cases instead of moving them to an advanced config page is never a good idea. How about an usable about:config alternative? "We designed a bad UI for advanced features... lets get rid of those features instead of fixing the issue!"