i do think this is something google does.
Because if you only sync once in a day or maybe 2 time a day. the syncs are working fine (basic calendar sync)

But if i up that counter then i also get server not responding and so on...

I think the best way woiuld be SyncML or if somebody makes something that talks to google through there api's and is then is a normal sync server point for the N900
Something that Goosync.com does.