IPhone 4 vs Blackberry push email--i.e. is the iPhone TRUE Push Email?

Question

considering hopping on the iphone train, however need to know something about push email that NOONE can answer (not even apple consultants at the store)!
issue: have blackberry now due to need to get emails and messaging immediately as it arrives in gmail and yahoo account, regardless of whether phone is asleep or not. can the iphone do this?
i keep getting the answer of you can go into account settings, select push, but then everyone is thrown for a loop when it comes to the push/fetch settings, i.e. 15 min, 30 min, hourly, manually, etc. e.g. no one can answer whether after the email is "pushed" to the iphone at minute 15 (if that is my setting), and i then get an email in my gmail or yahoo account at minute 16, if that email is immediately pushed to the iphone or i have to wait 'til the next 15 minute interval (or fetch it manually).
also, will the iphone wake from sleep to alert me to an incoming email as long as push is selected--regardless of other settings?
please help!!! and thanks in advance!!!

Answer 1

Apart from the "true push" aspect of email, one feature that is sorely lacking on the iPhone, one that for me is quite literally going to be the deciding factor to return to the blackberry, is the notification feature of true push email provided on the Blackberry.
I'm an on the go business professional. I manage several businesses along side my "day job." While my day job is the most critical, it has two facets and these have two different email addresses from different domains.
In short my device be it blackberry or iphone, has 11 domains address sending "push" email in various forms, pop, imap, and exchange. Of these 11, between the hours of 9-6pm 3 of these domains are absolutely critical that I respond within 15 minutes.
On the blackberry, I'm able to set sound profiles that will allow me to differentiate emails using sound by domain. So each of the 11 has a different sound tone as its alert. Without looking at the phone I can determine quickly if the message that was just "pushed" is of the 3 critical domains and take the appropriate action. Unfortunately, the iPhone doesn't have this feature, not natively, thus all mail gets the same tone.
I get about 30-40 messages an hour, it quickly becomes clear that I'm now tethered to the device just to weed out mail that is important, but not critical.
So factor that mail is not "true push" in all instances and that there isn't an ability to set unique alerts for the different addresses/domains, a great device is rendered inferior and an inferior device is heralded.
The apps that are available to address this, all require forwarding the mail message to a 3rd party. Not happening—Corporate would never allow or condone such.