Piper Jaffray analyst, Gene Munster, has released some statistics on the iPhone 4 launch. It turns out that 77% of purchasers upgraded, instead of switching over from another platform. This is not all that surprising given Apple's track record. Yesterday was their most successful launch to date.

What do the numbers mean? It means that Apple has developed a platform that keeps people coming back for more. However, it also means that Apple is living off of their fans and not necessarily converting people who prefer other platforms.

Here are some stats:

77% of the iPhone 4 buyers they spoke to were upgrading from a previous version. That’s up from 56% in 2009 and 38% in 2008. Last week, Morgan Stanley’s Katy Huberty predicted that the upgrade rate would be roughly 50%.

16% of buyers were switching carriers to AT&T, down from 28% last year

54% purchased the higher-capacity 32GB model, up from 43% last year

28% already owned an iPad

Of the 72% that did not own an iPad, 39% indicated that they would likely purchase one in the next 12 months