I did. I had three GMail accounts, deleted one, moved one to Fastmail, and now use K-9 mail for both the GMail and Fastmail accounts. Performance is great and d

I did. I had three GMail accounts, deleted one, moved one to Fastmail, and now use K-9 mail for both the GMail and Fastmail accounts. Performance is great and definitely no issues with battery life or missing emails. Google have recently put their regular email app on the Play Store, so it's possible to keep an apk copy for sideloading if K-9 isn't your preference. My only problem in the past was absolutely horrid syncing and GPS battery drain with Cyanogenmod. I keep going back to try, since first running it on my HTC G1 about 4 years ago. No other ROM gives me trouble, only Cyanogenmod. This is why I'm interested in a 'plain vanilla' as possible AOSP ROM. I'm back on stock 4.4 (rooted) and looking to move back to a non-gapps version soon.