Also am running Serendipity 6.4. Kinda worried to brick another phone so I don't wanna try the Kies update until I'm sure it works. I tried ODIN on my last phone but Kies wouldn't update it to Froyo at the time because of a different kernel placed on it by ODIN. Would love to see if I could just go straight to this update, but like I said, I'm a bit reluctant.
Yeah, I am feel your concerns and I think they are valid. You need to use the ODIN v1.81 if you do it. If you do it, let me know.
Do you have ClockWork Recovery installed? Is that what you use to apply the Serendipity 6.4?
Nevermind, I just found Serendipity 6.4 website. They use ODIN. It seems with ODIN, you could nuke your phone (As they stay in the instructors for Serendipity 6.4), and then follow the instructions.
Don't rely on my opinion though. I am not an expert on Android firmware updates with Captivate. I was with Motorola Backflip, but updating Captivate compared to the Backflip is different. With the Backflip I installed Clockwork Recovery on my phone and used it to update.
I am full time computer geek at work and an avid Linux user, but there are a lot of things with Android I am not familiar with and I would feel terrible if you listened to me and bricked your phone.