I've been having issues too. Email temporarily push, Facebook doesn't seem to want to push now either...
I just did a full restore today to try and get mbox mail to push (I created a topic but it appears to have been deleted) and I didn't imagine my native email app would be affected like this.
I restored to factory settings, jailbroke (first edition of the untethered JB) and then restored from my back up.
I am on 02 and am in no way hacktivated.
Edit: Facebook seems the worst. Just sent an email and it pushed immediately. Not sure whether this will remain consistent, however. Regarding Facebook, It just pushed too so I may be fixed
What I did was reset network settings and then fill them out again and do a hard reset (hold the home button and power button until the phone goes off)
Ok, I'll give it a go. Two emails failed to push whilst I slept so clearly there are issues. I imagine that setting my mails to fetch may work better when my wifi on my phone decides to sleep...?