Splinter Cell: Essentials is a terrible, terrible game.
The game takes off after the events of Splinter Cell: Double Agent. Sam Fisher goes to visit his dead daughter's grave a year after her death, and is arrested by the NSA and taken into custody. The guys who arrest him then remiscene about Sam's finest moments and heroic acts, and these flashbacks are played as missions. So there is no plot at all, given that the flashbacks have no connection between them whatsoever and there is no conclusion to the game at all; just flashbacks, more flashbacks, and even more flashbacks. Nothing is said about the start of the game, nothing explains what happens to Sam after he is arrested. It's like the developers were afraid to advance the story on a PSP exclusive.
The game's controls are worse than the relatively non-existent story. If there's a game that begs for a second analog stick more than this one, then let's hear it. But one can't blame it on the PSP's design, not after countless action games like Metal Gear Solid: Peace Walker, Syphon Filter: Dark Mirror and Resistance: Retribution have solved this problem by mapping camera controls to the face buttons. Splinter Cell: Essentials doesn't do so. You press the Circle button to go into camera mode and swivel the camera around, then return to normal mode and sneak around. This makes both sneaking and using the camera useless since there's no way to do both at the same time, which is very important and has always been implemented in the console games. Besides that, you use the same button to switch between goggles, which can get you killed or detected in the few seconds it takes to switch between them, and you use the right button to equip a gun. You can carry only one gun, and can't move while using it, which makes using the gun useless as well. The Up and Down buttons have no function. You use the analog nub to move. Unfortunately, it goes only between walking and running and there is no way to control the speed or angle of movement like in the console games. You can only move in one direction, and to change direction you have to let go of the analog nub and push it in a new direction. This makes sneaking around even more problematic. You can perform a SWAT turn between two back-to-surface enabled walls, but Sam gets detected by the enemy every time he does that, and this makes it useless as well.
Moreover, neither the graphics, nor the sound, nor the presentation are very good. In fact, all three of them are terrible. The menus are clunky, the load times take forever, the graphics are horrible, the textures are muddy, the music isn't tense even during the tense parts and there is hardly any music at all... there is no end to the things to complain of in Splinter Cell: Essentials. You're better off with the console versions.