I actually played Half-Life 2: Episode Two shortly after it was released, in October 2007. Like its predecessor, Episode Two continues the Half-Life story and provides another four to six hour adventure in which you battle the Combine as Gordon Freeman, sometimes on your own and sometimes with the assistance of Alex Vance. As an installment, I enjoyed Episode Two a little more than Episode One - I thought the levels and environments were fun and a bit more varied, and the pacing was just right.
I thought the ending with the timed Strider sequence was too difficult, though, and could not beat it initially. After two dozen or so tries, I gave up and only tried again recently when I replayed the game. My luck was no better the second time through, and I ultimately resorted to cheat codes to finish the game, one of the only times I've ever done so. My difficulty with the ending is the reason I did not blog about the game after first playing it, and am only posting now, following the replay.
Overall, I remain a huge fan of the Half-Life franchise and still rank the original Half-Life 2 title as one of my all-time favorite games. However, sitting five years from the 2004 release of Half-Life 2, I think it's past time for Valve to get on with it and release the final episode (Episode Three) and conclude the three-part sequel, if only so they can start making Half-Life 3 or whatever will be their next big game. The serials were an interesting idea, but, in this case, it's simply been too long between installments.