zektor has released a supposedly safe firmware updater, read the quote for his release notes.
This is based off of my offline guide to upgrade any console to v4.2 safely. This is a modification of the Shop Channel and IOS61 Installer by tona. It has been rigorously tested and should not brick anyone, but as usual, use it at your own risk. Source included of course.
It will detect your region, download and install all of the NECESSARY IOSes, your specific system menu, and the shopping channel update from v4.2 It will NOT touch your cIOSes, stub anything, or touch your boot2. It also will NOT trucha sign any of the IOSes it downloads and installs. If you want to pirate, you'll have to go ahead and use DOP-IOS or similar to trucha patch your IOS70 after the upgrade is complete
It is almost completely automated. Answer a question in the beginning, sit back and relax, and wait for the update to be completed. When finished, you'll be on v4.2 with everything functional (no upside down HBC, no "vulnerable IOS not found" errors). This should hopefully eliminate all of the goofy issues people have been having with the upgrade.