Thanks Steven and Tony,
It is no doubt an extremely challenging set to complete. I have been working on it for close to 10 years. My first card was Walter Johnson, which is maybe the ugliest card in the set...there are other contenders no doubt
...and one of the very few major HOF'ers. As far as the toughest card, wow, there are so many. I have tracked the set pretty closely for a decade and there are at least 20-25 cards that I have seen come up for sale individually less than 5 times in that time frame. I'd say that a good half of the set is pretty scarce. There are several great threads on the cards that people find the toughest.
It was very interesting to see nearly an entire set presented individually like this, because you get a pretty good idea of the market on several of these that come up rarely. Most of the prices I thought were very strong, but a few cards that I consider among the toughest didn't sell for nearly as much as I anticipated. I guess it's mostly a matter of a few collectors seriously going for the set and just the coincidence of which of the tough ones they may need at the time and bid for against each other.