It is truly push. I tested the heck out of it. My Droid, PC and iPhone all receive the email, sent to the gmail account, within .5 seconds of each other.
To get true push on a gmail account, you have to set it up properly.
1) Settings
2) Mail, Contacts, Calendars.
3) Add Account...
4) Microsoft Exchange
5) Fill in EMAIL, USERNAME, PASSWORD and DESCRIPTION ONLY
When you hit next, it will query the system and then present a new dialog
6) Server - Put in - m.google.com
7) Save - And that is the hard part done.
8) Go back to the list of accounts.
9) Fetch New Data
10) Push - Turn it on.
11) Advanced - Make sure you have the accounts set for PUSH that support it.
Exit settings because you are done.
I have also tested PUSH support for Hotmail and Yahoo. AOL does not support PUSH at this time.
Now I know a lot of you are going "But there is a GMail specific add account". Yes there is and it is PULL only for mail. I tested it.
I use Google for Contacts, Calendars and push mail on a daily basis. If my wife (Droid X) or I (iPhone 4) enter a contact or calendar item the other phone sees it within 5 seconds usually.