Thanks for the replies folks!
Well I did everything right: floated him in the tank (inside his cup) for about 3 hours, added some tank water to it gradually, and didn't add any of the cup water to my tank. I have been keeping fish for over 2 years in planted tanks so it's not like I'm a newbie at this but I thought maybe acclimating a Betta was different, that maybe this type of fish had different requirements than other fish.
I guess the only thing I did wrong was to get the fish just before the weekend and not having medication on-hand. I live in the boonies so getting supplies is rather difficult on weekends. Had I had some medication on-hand already the poor fish may have had a fighting chance but as it was the disease developed too quickly for me to be able to get anything to help him out.
I am still on the lookout to add a Betta to the tank. There are currently three Oto cats in there keeping it somewhat clean and I'm anxious to get the main attraction in there (the Betta - that's the whole reason I started this tank). This time around though, I bought some Maracyn and some Ick medication... I want to be ready should something come up!
Here are some pics of the tank and the poor little guy who didn't make it...
In this last pic you can actually see the patch of white fuzz in its early stages just between the ventral and anal fins of the fish. Towards the end, 48 hours later, he was covered by it...