The biggest thing to watch out for is that many of their discounted economy fares absolutely prohibit any type of standby travel, which is significantly different policy from the other carriers. (Nearly all other carriers will allow same-day standby on discounted airfares, even if they put you at the bottom of the list.) If your travel plans need to change for any reason, you will wind up hating this airline (unless, of course, you've already bought full-Y or first class).

I think this airline is trying to really distinguish the service it gives to its highest paying pax by both offering additional benefits to full-Y and punishing discounted coach flyers anytime they can.

Having said that, I do fly TWA from time to time and have found that I get more miles-per-dollar here than anywhere, thanks to some pretty good bonus offers and higher minimums on short flights. Redeeming FF miles is always a challenge, but TWA isn't much different from American and Untied in that regard.