For the most part, this game delivers on it's promise: 3.5E D&D in the palm of your hand.
I think that D&D Tactics hits on more cylinders than it misses. Not all of the options open to the PnP gamer are there: No tripping, no disarming, no grappling, Greater Invisibility doesn't work properly, Sneak Attack damage seems to work even on undead, etc. However, the meat of the system is all there and one can try a variety of moves to dispatch the critters. Flanking (arguably the most important tactic in the game), feinting, charging, combat casting, attacks of opportunity (arguably the most vague concept in the game), tumbling, and 5-foot steps are in the game.
The UI in the game is not the greatest, but serviceable. I only found myself cursing it once or twice to eternal damnation. Movement is pretty tedious, but mostly that tedium applies when not in actual combat rounds. A method for moving in formation or all PCs at once when not in combat would have been most welcome.
The story itself is not that bad and there are no really surprises in the plot. Which is fine by me. Some of the JRPG tropes of plot reversal get a little hackneyed and tiresome. The campaign is rather easy however and heavily balanced in favor of the PCs. You will be 3-4 levels higher than the recommended levels for each adventure from about halfway through the campaign onwards. You can remedy this yourself in a couple ways like using less than the allowed number of PCs or purposely not leveling PCs. But the designers should have had a better handle on this to begin with and made the later levels a tad more challenging.
One final piece of information of note is that knowledge of the D&D rules is essential to get the most from this game. Owning a copy of the Player's Handbook or a link to the D20 SRD (http://www.d20srd.org) will help the player immeasurably. The manual is vague on most things, but what are ya gonna do? PSP cases don't leave room for an awful lot of manual. The info available in game is pretty complete actually, but not the easiest to read because of the UI design.
To sum up the game, while not perfect, is an enjoyable way to play D&D on the go. It's more in depth than any other S/TRPG out there on a portable or even console for that matter. There's just so much more a character can *do* on any given turn than say in a game like FFT or Jeanne D'Arc (both of which are excellent too).