I was able to get the N900 this finally sync my contacts and calendar, but I have the same issues you are experiencing as well.

I noticed my original issues with emails because I have an account with 5000 emails and it would lock up when I launched the email app and tried to immediately scroll through them. The email app would crash. So, last night I launched the email app and loaded the account then let it sit over night. In the morning everything worked fine.

Why does the N900 not down load the messages and store them on the device instead of downloading the whole account each time when launched?