Well, I think the general consensus here is that Infinity Ward struck gold again. Every person will have their own personal issues with the game, but overall, it’s a well balanced and well developed game that will likely garner many Game of the Year awards.
SoapyTarantula had this to say about Modern Warfare 2:

The long awaited sequel to what was, in my opinion, one of the greatest games I’ve ever played, has arrived. Call of Duty: Modern Warfare 2 comes out swinging with every punch hitting its mark. Modern Warfare 2 takes place five years after Call of Duty 4 with you playing as a handful of characters throughout the six or so hour bad guy shooting, plot twisting, incredibly fun, campaign.

The updated Call of Duty game engine does well to increase the quality of the graphics and gameplay. New abilities such as using two weapons at once and Predator drones loaded with missiles allow for interesting new tactics to be used.

Graphics are done very well, while not a big boost from Call of Duty 4, they are still magnificent. The draw distance is much farther, so in multiplayer the Ghilie suits work very well. More detailed textures clean up most blurry pixels at close range. My favorite addition graphics-wise is the glint of scopes. It’s incredible to be able to pick out a sniper hiding in the grass, almost perfectly camouflaged, because you see a flash of light from his scope.

Sound design is excellently done. Having personally fired a few of the weapons featured in game, they sound exactly like the real thing. In the campaign your squad mates will alert you and each other to enemy positions, if they need covering fire, or if they get hit.

There are plenty of new weapons and equipment items to choose from in multiplayer, along with new kill streak rewards and the introduction of death streak rewards, which are intended to prevent players from getting what is known as ’spawn camped’. New kill streak rewards include Predator missile strikes, Harrier air strikes, Pave Low helicopters, being an AC130 gunner, and a tactical Nuke, which wins the game for your team. Death streak rewards include having extra health for a few seconds after you re-spawn, dropping a grenade after you die, or stealing the class of the last person that killed you.

The campaign itself is incredible, with no filler missions. The campaign kept me interested at all times. From climbing an icy cliff to fighting in Afghanistan, you aren’t going to be bored.

Modern Warfare 2 is an absolutely amazing game, if you are wanting to get into First-Person-Shooters, pick up Modern Warfare 2. If you’re a gamer, pick up Modern Warfare 2. If you are breathing, pick up Modern Warfare 2. Call of Duty: Modern Warfare 2 gets my vote for game of the year.

Dez1013 seemed to like the game too.

First off, I’m pleased that this game provides lefty controls (not sure about legacy for those folks) and the option for southpaw trigger controls which to some is more comfortable (like me).
Regarding the length of the campaign I’ve heard some complaints but I feel that its so good you get sucked in and next thing you know you’re finishing the game. The AI is much more improved, actually working against you instead of just spewing 2 tons of lead at you while standing still. It’s actually tough fighting an AI that wants to flank you and move to better positions and makes for a more enjoyable and unique experience each time the game is played.

The spec ops missions are a great addition. Letting you play the parts of the game you enjoy most in fun scenarios that can be done co-op and really do require teamwork to win.

The multiplayer is superb. More weapons and better choices for secondary allow you to make multipurpose builds easier than the first MW, now allowing you to spray tons of lead and still take down a chopper, or snipe and protect yourself at mid range. The new maps are much more spaced and allow for more gunning less nading. The only maps which are generally disliked IMO are the Brazil based maps. The riot shield really helps for objective games allowing players to cover themselves and others in those open flag areas. Disappointingly, the lack of a cohesive party system where the leader can bring everyone with him or her still makes for a frustrating time. Ground war is much smoother now and with the removal of frag x3 you can safely walk around without dying a frag death every 3 seconds.

My own review of the game can be found over on my personal blog.  With few exceptions, it seems Modern Warfare 2 has jumped to the top of everyone’s most played list lately.  It has a great multiplayer system that only seems to be lacking in a few areas.  Some gamers have already found glitches, which Infinity Ward is actively working on fixing through update patches.  Overall, it’s a great game.