I have this 'problem to?. I can live with it but I have the ProfiMail licence. so I'll probably transfer it to my Galaxy Nexus.
With ProfiMail push mail workes great as the one would expect. I get messages instantly, usually even before they appear in chrome with Mail Checker Plus extension set to refresh each 15 sec.
With Google Sync I have a feeling that messages are pooled in intervals of 10 min or so.