The latest "official" release is the one that should already be on your phone: ROM 1.35.255. This is a AKU 2.3 ROM by leaf btw.
Leaf says that they will ship their official upgrade to AKU 3.3 in March. In the meantime, if your phone is working 100%, there is no real reason for you to change anything.
Now, I can give you the link to an exe file that will automatically update the firmware to the AKU 3.3 test ROM, but you don't really want to do it that way. By just running the exe, you lock your radio bootloader, and can no longer downgrade or upgrade you radio stack. This is bad news because radio stack 1.27 is the best one, not 1.34 that comes with the full exe ROM upgrade.
Therefore, the best way to do it is to unlock the phone, extract the necessary parts of the new ROM, and flash the EXT ROM and the OS separately. This is quite a procedure. Not difficult, but rather long. And if you make a mistake you're stuffed.
IMO, unless you WANT to be technical and play around with your phone and don't mind the risk, leave it as it is until the official update comes out.
For those of you that are having issues with dropped calls & poor reception, upgrade the radio stack only for now. Let me know, and I'll run through it again if you want.
Those of you who MUST tinker with the phones, the test AKU is pretty nice. Shows E for Edge, U for UMTS and H for HSDPA. Is a bit faster, the modem utils is a bit better, and other small stuff. not a BIG change, pretty cool nonetheless.