Well, turns out interrailing hasn't completely bitten the dust, though it has become a lot more costly. According to the ropy English of the official website, Europe (now expanded to everywhere except the former Soviet Union, Serbia or Albania, but including Morocco) is split into eight zones; you can get a 16-day ticket for one zone for €210, a 22-day ticket for two zones for €289, or a month-long ticket for all eight zones for €399 - that's if you're under 26; we old folks pay 40% more. Strikes me as rather expensive, when you can have a week in the Canaries for a third of that. The two-zone ticket seems like the best value though.
For Americans there are various alternative options including the Eurail pass which is staggeringly expensive, even with the cheap dollar of today, and doesn't even cover Eastern Europe - or the UK. No wonder it's got less popular.
I do a certain amount of train travel even now - often by Thalys to Paris (and once to Cologne), sometimes by Eurostar to London, and last year overnight to Berlin and back. It always brings me back to those days of juggling the potential discomfort of yet another night on the train versus the cost of a night in a youth hostel. And of course the thrill of travelling with your girlfriend - "Did the train move for you, dear?" as we used to joke. But enough of that.