In all honestly if I could go back before my purchase knowing what I know now, I'd pass and continue playing MW3. I consider myself to be a pretty big CoD fan - I have multiple copies of all the titles for my collection since the release of CoD4, including purchasing the console bundles (both 360 and PS3). I went to CoD XP and took vacation time for both MW3 and Blops 2 (huuuuuuge mistake for blops2). I put in over 300 hours into MW3 and double that into MW2 since it's my personal favorite.
Traditionally, between Infinity Ward and Treyarch, the latter tends to make very few drastic changes to their titles. If you haven't been following the news, they are being quite harsh about the feedback and just revert to their 'my metrics say otherwise so deal with it!' attitude. Check this topic itself, the official Xbox and PlayStation forums, and the official CoD community forum and you'll see that the biggest complaints will center around lag compensation and spawns, and Treyarch's done jack shit about either.
It obviously all comes down to your playstyle. I cannot, absolutely cannot stress enough that this game is pure SMG run 'n gun. Despite being a huge fan of the series, this is hands down the worst CoD to date, IMO. If I were you I'd put the $60 into another title like Assassin's Creed 3, Hitman: Absolution, Battlefield 3 Premium, Halo 4, etc. I know 2013 is looking somewhat bleak in terms of games, but even if you absolutely HAVE to have that multiplayer experience until the next best thing is released, I'd stick to playing one of the previous CoD titles. Depending on your platform of choice, MW3 and the first Blops both still have a healthy pool of players left.
You can find the patch notes
here. This patch was basically a gimp patch for the most part, adding recoil to all SMG's and the decent AR's.