The retail Sony Xperia Z (C660X) and Xperia ZL (C650X) units around the world hit the market with firmware version 10.1.A.1.350. This brought Android 4.1.2 Jelly Bean and 3.4 kernel. However, it looks like a new version is rolling out to Xperia ZL owners in Estonia and Russia. Firmware version 10.1.A.1.434 is still based on Android 4.1.2 and there don’t seem to be any notable improvements over the previous firmware from initial comments.
This version hasn’t been certified on the PTCRB website yet. The C6503 (European/Asian LTE) variant of the Xperia ZL has firmware 10.1.A.1.350 listed, whilst the C6506 (US LTE) variant has firmware 10.1.A.1.395 listed. If you have updated to this latest firmware, please let us know what differences you found in the comments below.