I've never been through the Channel Tunnel before, but on Tuesday, I got the good news that I was needed at an all-day meeting in Ghent. Last minute flights and last minute EuroStar cost about the same, and the theory was that we'd be more productive in transit on the train than on a plane.
Did the theory work out?
For the most part, yes. The train was immediately better than a plane because you only have to go through passport control once (once you've gone through in London, you're in the Schengen zone, and once you've gone through in Brussels, you're effectively back in the UK). It also lacks the tedious restriction on liquids - no more putting things in a transparent plastic bag, no more buying tiny cannisters of deodorant, no problem bringing back Belgian beer!
We went in "standard premier" to have a bit more space, and it was about as spacious as first class on most UK trains, with a power socket for each seat (half of them are French/EU two pin plugs, of course, but you probably had your adapter with you anyway...)
The food and drink was also much nicer than you get on a plane, and you have to turn up less in advance and hang around for a shorter time.
The only thing which surprised and disappointed me was the crap internet access. OK, so it was an improvement over most short haul flights, where you're cut off completely in the air, but I was amazed at how poor the mobile coverage was along the route. I didn't manage to keep a connection up for more than about ten minutes at a time,
Then again, getting from London to Brussels in less than two hours is pretty damn impressive, and being able to buy tickets which cover onward travel to any Belgian station was the icing on the cake.