Firefox 4 beta does work on the Xperia X10, but it does not work on the Xperia X10 Mini.

You must upgrade your Xperia X10 to Android 2.2 before installing Firefox.

For more details, see https://wiki.mozilla.org/Mobile/Platforms/Android#System_Requirements

Unfortunately, no it doesn't work, i've just installed in my fresh new x10a which i received by the morning, actualy firefox was the first thing i did install, but once i've ran firefox my phone locked and crashed and got into a forced reboot. Tried again and the same happened.

I hope this gets solved.

I love firefox since 5 years now.

Very disappointing... Web surfing without Firefox is not the same... I've read some news that Sony will upgrade X10 family to Android 2.3 - which are excelent news. We'll have to wait until October to find it out, though... Too bad!

Android 2.2 is not available yet for Xperia X10 so I don't see how you could say Firefox works???

I can't even download it yet! Very much wish I did though.

Firefox will run on Android 2.0 and higher, so you can install it if your carrier has published an Android 2.1 update for your X10 phone.

(However, many users have reported problems running Firefox on the X10, which we still need to investigate and fix.)