Honestly, I think Halo 4 is as close to perfect as it is possible to be with a game that has such a huge multiplayer component. ALL games have bugs and glitches, but I've experienced very few personally.
And the campaign and Spartan ops are just awesome. The story is easily the best in the Halo series IMO, and I love Spartan Ops and cant get enough. Really hope they do atleast one more season.
Cant wait to see what 343i does with Halo going forward. After how great Halo 4 turned out, im sure 5 and 6 will be amazing. And hopefully they do release Halo 2 anniversary, even though Im not a big fan of Halo 2 overall, it'd still be nice to have it on 360 or the next Xbox.