Since yesterday 27 Feb, push mail notification on Android is extreme delayed. Automatic sync seems to work only temporarily. It all started when I found a new button on my phone/tablet "Google settings"
The delay issue occurs on tablet and phone, ICS and JB, 3G/WiFi the same behavior. I have root access and checked if push notification works (prog available in GPlay). It does.

Is it only me?

The wife or I haven't experienced any delays on our two Samsung phones, Samsung tablet (not rooted), or Onda tablet (rooted)...and I have 3 gmail accounts and the wife has 1. Maybe it's your mobile data and/or wifi internet connection? We are on DTAC 3G and for home Wifi True DOCSIS/cable.