I got the 32G HK version of iPhone 4 when I traveled to HK around 8/13 (ordered online from Apple HK store on 7/30 or 7/31, the first day it's available for $ 5,888 HKD). It's been great! Since I live in the US, having an unlocked version is really helping me a lot if I need to travel to Canada, Taiwan, or HK for that matter. I can just get a local phone number and use it at will...
I purchased a 3HK prepaid card with Data plan for $98 HKD when I got the phone, and it lasted the whole 4 days I was in HK, so I think it's definitely worth the money if anyone will be traveling to HK for a short time and need a local phone number and data plan...
Back to iPhone 4. Been using 3Gs in US (locked version until recent published JB), and now I can tether in either 3Gs or iPhone 4 (the locked version of iPhone 4 has limitation on tethering from AT&T as you need to sign up for extra monthly fee in order to tether with iPhone.) So I think it's definitely worth the price difference of 438 USD.