Could have been alot better.
The best aspect of IW is the storyline. Understandably not as good as the original which featured all kinds of interesting conspiracy, it nicely picks up where the original let off. You will revisit old characters and locations so in this respect those who have not played the original may find the plot unintriguing.
The graphics have been vastly improved and the environments are excellently layed out and detailed.
One of the largest flaws is the RPG element has been stripped down though and it does affect the game greatly. Now, instead of having skills and biomods (bodily enhancements that give you special abilities) you are left with only the biomods. Also the money system seems to be under used. Occasionally you find someone who will sell you something, but total its maybe a half dozen characters that will take your credits.
Another drawback is the ammunition system, which is one of the most complained about parts of the game, deals the game a serious blow.
Instead of having pistol ammo, rifle ammo, smg ammo, you have a "universal ammo" which all weapons use. The best way I can describe it is the ammunition is mana, and the weapons are your spells. So if you run out ammo with the pistol, you have run out of ammo with every weapon (not to mention it seems you cannot carry very much ammo). So it can be very frustrating to be battling some of the games tougher opponents.
Overall, fans of the series will find it to be a nice continuation with a few disappointments, but those unfamiliar with Deus Ex will find it frustrating and a struggle.
A third game might be nice though. . .