I updated to 4.2. Then I wanted a new phone.
4.2.1 came. It solved 5% of the lagginess.
However, it was still unbearably slow. With 4.1 I had an amazing phone, 4.2 made me want to shoot it.
But after 4ish weeks I found something out… Go to Settings and then Sync, click the Google account(s). Disable Google Currents syncing.
Enjoy. You might want to reboot to be sure, but for me this brought my phone back. It’s not perfect, it’s still a bit slowish, but it’s a lot better!