I’ve never been a fan of Samsung’s touchwiz. I find it a bit fisherprice if I’m honest, clunky and a not particularly quick. The stock dialer, contacts and messaging apps on the Galaxy S3 are, if I’m completely honest, rubbish. They’re slow. I’m quite demanding when it comes to mobile phones, they need to be instant for near all actions. I had been running a custom touchwiz-based ROM on the S3 and replaced the dialer, contacts, messaging and keyboard apps with replacements. Thankfully now that the CyanogenMod nightly builds have become stable enough and pretty much feature-complete I’ve blown that away and I’m running with CM 10.1 as my daily driver. This means I have a stock Android 4.2.2 build running on the S3 and it simply blows Samsung’s own ROM out of the water. The only two replacements I’ve put in are the launcher (replaced with Nova Launcher Prime) and the camera (replaced with a port of the Huawei camera that works even with the flash enabled which stock camera does not). The CM team have worked hard to iron out as many bugs as possible and the ROM is really coming together nicely. There was a leak of the 4.2.1 Samsung ROM recently which allowed the latest drivers to be ripped and ported so that has helped with GPU performance.
If Samsung would just pull their socks up and sort out the shoddy performance of their customised apps then I might consider moving back at some point. Its nice to have the choice though.