Lucky points out today that Amtrak is moving to a revenue-based model for its points program. He's also reporting that they may leave as a Chase Sapphire transfer partner. Though I suppose if they do the former, I would never need to do the latter...
Like most of these programs (Virgin, JetBlue) the points will very likely end up being worth 1.3 - 1.8¢ each, far below some of the better rates you can get now. On Acela express, I've routinely redeemed in the 3 - 4¢ per point range, which is better than most domestic airline redemption rates. As Lucky points out, there are even better redemptions available on long distance sleeper cars.
I guess the one positive is that they'll hopefully get rid of those pesky blackout dates.
UPDATE: more info from Amtrak here. Analysis here.