Go to settings > Accounts & Sync. I have here enabled Background data and Auto-sync. Underneath you have your accounts such as facebook, google, news, etc. Under google I have all of the options check (contacts, gmail, calendar). My google calender syncs virtually instantaneously when I adjust events on my phone.
Added note, if you want your various calendars to be viewed with certainty as different colors on your Aria, you need to choose the color schemes in a horizontal array from your PC on google calendars.