The 10000m is going to be the most interesting race for me because (a) there will be suspense over whether guys can hit the 27:45 Worlds qualifier and (b) it will give a preview of how the contenders will stack up for nationals with two spots up for grabs.
Curtis, True, Bumbalough, Mead, Shrader, Estrada can all have legit hopes of making the team going into this race.
Rupp vs Hill/Lomong in the 5000 is the sexy matchup but you pretty much know they will get the qualifiers and, whatever happens, they will be top favorites to make the team (along with Lagat).
The 1500 field is certainly very good but the guys who are the chalk to be the top four for nationals (Centro, Leo, Blankenship, Casey) aren't here.
So the last race of the night figures to have the most intrigue.