Are you blazing through Alias as well? I never got more than a few episodes into S4, and was curious how it all panned out (though "not well" seems to be the general consensus).
I wouldn't call Through the Looking Glass a bad episode or anything, I'm just not sure there were 2 hours worth of content in there. All the buildup was great, but the last episode didn't have me hooked, minute-to-minute, as the previous finales.
Alias, well, heh. I do like Alias, but the problem is that I'm the sort of jerkoff that has to consume and understand every line of dialogue in a show. Since (in at least the first season) Alias is filled with the spy-equivalent of Star Trek-style technobabble at a West Wing dialogue pace, I find myself frequently rewinding so I can try to understand lines that are filled with meaningless acronyms and what not.
I like watching TV while I WoW, and since Alias requires me to parse lines for both meaning and thematic flavor, I won't do the show the disservice of watching it while occupied with something else.
(Also, I already watched the first 2 seasons. First season I loved, and the second I half-loved. I didn't like the mid-season reboot that the series obviously got.)