The C6 hasn't got its proper section yet, so I'm posting this here since the C6 is very close to the 5800.
I configured my Gmail on my nokia (just had to enter my e-mail address and password) and it works fine.
Only thing is, syncing doesn't seem to work as it should. When for example I read Gmail messages on my computer and delete them, then that's not synced to the phone (said messages remain in my inbox, unread status). Also, when I delete messages on my phone, I can't find them in the deleted messages folder when I access my Gmail on my computer.
Even when I force my phone to sync (when in Gmail --> options --> sync now), nothing seems to happen.
Today I discovered m.google.com, which offers some mobile apps. Would it be better to just delete my gmail account on my nokia and install the different apps from google directly (which would give me calendar syncing as well ?) ?