The casting was great, imho. I agree with all that you said about the characters not being likable, but I do think that the actors just really meshed together well and made the characters work as a group, eventhough I didn't like 3/5th of the group either (My 3 would be Barney (I know he is a fan favorite, but I'm just not buying the "likeable womanizer"-trope), Lily and Robin). I thought Ted worked well, by being fairly bland and "fairly" inoffensive, as a grounding character of the show, even if it's creepy that he told his children about all of his "romances" he had, including one-night stands and attempted threesomes, which really destroyes his portrayal as a "hopeless romantic". Man...now that I read my own thoughts about those characters out loud to myself, I wonder why I watched it for so long also. Those actors did one heck of a job to make that stuff work. Do you know, a spin-off is in the work called "How I met your Dad"? No, it isn't a show from the perspective of the mother, that could've potenitally saved the HIMYM retroactively and would've made too much sense.