There are regular questions on here about travel options between Spain and Portugal, so I thought it'd be worthwhile to report on my recent experience taking the overnight train between the two countries.
Facts:
There are two daily overnight routes between Spain and Portugal: Irún-S Sebastián-...-Lisbon and Madrid-Lisbon. I took the former from San Sebastián last week, but my comments would apply to both as they use the same train sets. Prices are fairly low in shared 4-berth couchettes, but my partner and I "splurged" 269€ for a private 2-bed sleeper with sink, one way. About in line with high-season plane fares.
Pros:
- Very comfy beds (not for people taller than 6' though)
- Excellent food on board. Really. And very cheap, 10€ for a main course.
- Punctual and time-efficient
- Sleeper compartment is of a fairly good size
Cons:
- The train sways and the track is quite bad, I was woken up a few times by the jolts.
- No control on the AC, which started out very cold, then got very hot, then became acceptable
- Depressing compartment in day mode (seats aren't great, windows are small)
- Old and frayed rolling stock, reasonably clean though, with spotless sheets.
Verdict:
Worth considering if you're looking at a way to go from the Basque country or North-Central Spain (Burgos, Salamanca...) to Lisbon without wasting too much time in transit. Fairly comfy but don't expect the best night.
And I guess that booking early for the berths in 4-berth compartments would provide better value than what we got - prices can be below 50€, at which rate it is even cheaper to privatise a 4-berth than to pay for a 2-bed sleeper. Not sure if the berths are as comfy as the sleeper beds however.