Hopefully there will be no problems. Some people already use Firefox with Windows 10 pre Release versions.

There should be a 64bit version of Firefox for Windows available later this year, but until then the standard 32 bit for Windows Firefox is what should be used.

It is currently buggy. My neighbor made the mistake of upgrading to Win 10. She has firefox 42.0 (despite my telling her like 5 times DON'T UPGRADE) (She is computer illiterate and WAY TO TRUSTING)

1. It lags major in searches. actually all 3 on her browsers does Firefox, chrome, IE(new one)

2. I could not access my library account, I just get the activity circle on the tab. Waited 5 minutes and gave up. (I did it from my windows 7 rig and it logged in in seconds. to confirm it was windows 10 at fault, we both use firefox 42.0 I have a bunch of addons on mine.)

3 Bookmarks menu as mousing over the different bookmarks it will randomly highlight book marks and stay highlighted, Then you start seeing doubles and it goes blurry on all the book marks

4. Switching to high contrast theme seems to speed the searches up a little. but not consistently.

5. bookmarks are opening quickly.

6. The browser is not being rendered completely after switching to high contrast theme(windows high contrast). For example the the search button next to the search box does NOT display. When clicking on the spot where the button is suppose to be it randomly works, despite not seeing the button at all during the entire proccess.

7. when mousing over bookmarks it opens a box that says what it is that your moused over, that is blank. Every mouse over without exceptions.

8. She only has 2 addons ghostery and adblockerplus

9 firefox is set to default install settings for all things except privacy which are set to to most private settings.

I am not really looking for suggestions Like roll back to windows 7, I don't want to do that on her computer because she does not possess the original OS. If it gets messed up in the rollback or needs OS product key at some point it will fail in the rollback.

I am adding this as cautionary to those who have not upgraded to windows 10. Windows 10 as of 12-15-15 has some serious issues with browsers (even its own) and connection to the internet issues of the activity indicator running circles or not doing anything for extended periods.. Or not displaying the browser correctly or not being able to access certain website locations etc.

The above mentions on bugs and such that is only what I actually used I did not check other features like history and such. I was just trying to get it to do the most basic stuff that my neighbor actually uses since she is unable to tell heads from tails on almost everything computer.