I'm planning to travel from Madrid to Lisbon about the 25th of feb; going by train, returning by plane. Any experience with the train ride? station, cost, ticketing, journey, border, station in Lisbon?

If you go to the transportation forum and use the search function for "Lisbon", you will find plenty of information.

Lisbon's Oriente Multimodal Transportation Center (Oriente Station - at Expo'98 site) is more traveler-friendly and conventienty located: Lots of fast food restaurants and ATM's (what you will need).
But for Feb 25, check out Spanair's Ofertas: That's the low season and they may have some pretty good sales for roundtrip travel http://www.spanair.com
Used to be you could only find their ofertas on the Spanish language version

Thanx Eddie for the Spanair tip. They are more expensive for my travel dates BUT, get this......if you can leave Madrid on Saturday morning, the ticket is $141 roundtrip. Otherwise it's $462 round trip.

So, I'll be taking the tren hotel and returning by Iberia flight for $151

I'm flying on Air Europa in early March from Lisbon to Barcelona for $75 - you might want to check and see if you can find a cheaper ticket with this airline.