There have been several threads on Talk about this, including the long winded one started by Vitaly Repin. The short of it all: MfE on the N900 does not officially support Google. A business decision by Nokia, and unfortunate for many of us Maemo enthusiasts who happen to use Google's services for basic PIM.
The service offered by NuevaSync is free (for basic usage), and provides a nice bridge between the N900's MfE client and Google. I am a NuevaSync user for about 2 days now. I have not used it to sync e-mail, but Calendar and Contacts sync like a charm. The free account allows you to sync calendar entries up to 2 weeks in the past. If you are like myself, and have years of calendar entries that you want to sync once to the N900 (to retain your calendar history), you will have to 'try' a premium account for 5 days to get past the 2 week sync restriction that NuevaSync has in place on the basic account. The premium account has other niceties, but for me, the basic account is just enough.
It's another service to add to your already large list of accounts you manage. But if you use Google like I do for almost everything, then NuevaSync is a must for your N900. As I posted on Texrat's blog, I hope that major 3rd party services (such as Google) work out of the box with the first MeeGo product from Nokia. I want to be able to open the Harmattan device's box, fire it up, and connect to my entire online life in a few minutes - 100% reliably, and using the default clients. Hopefully, my dream will be a reality shortly!
Note: I am in no way affiliated with Nuevasync.