Just wanted to say that I was I was able to root per the Odin method defined here (on the original post [OP]) to my Android 2.3.5 (Kies updated before unlock) Samsung SGH-I897 Captivate with success.
But it took me many times until I finally installed Busybox app. off of the Android Market via my Wifi connection. Perhaps it would of taken me longer to figure this out, but I had installed the Galaxy S Unlock app (also from Android Market) that I would try to apply. It would give me a Busybox error which was the hint I needed. So even though I ran both Odin PDA updates as defined in OP, I didn't have to repeat the Odin tasks once I installed Busybox.
I was rooted. All I had to do then was to run Galaxy S Unlock and this time I was able to perform all three "Galaxy S Unlock" steps with success (most importantly, the backup step and finally step (3) which was the
Unlock step). This root method was a no-go until Busybox was loaded on my phone. Yes, I was rooted and unlocked. My T-mobile sim card now runs on the phone (Android Gingerbread [v2.3.5]) which was originally an AT&T phone.
Even though I was successful in getting this Captivate (bought used off of ebay) to work with my T-mobile SIM card, I now wish I just bought an original (but also used) T-mobile phone (e.g. a T959 Vibrant
*). For a T-mobile user
T-mobile phones (Android 2.2+, some Blackberrys, see link below for a longer list
*) have their Wi-Fi Calling app. (UMA technology) that provides a seamless/automatic alternative connection to the cell phone tower pathway where wifi access is available (e.g. at home, hotels, etc.). Imagine if you were at a hotel that had dead cell coverage for your phone but you were able to connect to their wifi. You would be able to make calls!!! I had this experience and was able to plan/reserve my next night's stay while visiting the Sequoia National Park without being horrified ($$$) by using the hotels phone to make numerous outbound calls.
* http://smart-wi-fi.com/smartphones.php