I have CyanogenMod 11 installed of my Sprint S3, and I love the ROM overall -- stability, controls, interface, customizability -- but there are two serious deal-breakers with CM11:
1.) Signal quality is terrible. I've tried the mods to flash different baseband/radio/modem firmware and it didn't help. I went from 3-5 bars with the stock ROM to 0-2 bars with CM11. Calls often won't even ring, and the first thing I hear is the voicemail notification.
2.) This is probably at least partly related to the reception issue, but not entirely I'm guessing. My battery life is downright miserable. With the Sprint stock ROM, the phone could last 2 days on a charge in a pocket or 16 hours or so with heavy use. With CM11 using the strictest processor speed cap, the most conservative performance settings and the Greenify app, I can kill the battery in 2 hours of heavy use, or 5 hours pocket time.
Can anyone recommend a good, solid KitKat-based ROM for the S3 with features similar to CyanogenMod, but with better reception and battery life?
Read more: What is a good Kit Kat (Android 4.4) ROM for funtion, batthery & signal for the Samsung Galaxy S3?