Maybe worthwhile once in awile, but a bit of a hassle! I used to do SEA-YYZ on Thai quite often in the early 1990's, for cheap - $300CAD or so, but after about 4 or 5 times, it drove me nuts. The service was quite good though! It was on a US-based TG A310. Alaska did SEA-YYZ in 1991-92 or so too, but only briefly.