This game is nothing more than a unique but simplified Tetris clone. There are very few, if any, advanced tactics other than setting up combos, remembering horizontal, or sneaking pills underneath viruses. It won't take too long to fully master all of these tricks. After that, it's only a matter of speed. Unlike Tetris, where you have to worry about somewhat strategic placement of pieces, there's usually fairly obvious places to put the pills. There's very little need to worry about covering up viruses (much like creating "holes" in Tetris). It'll happen, but it's quite simple to get out of it. For the most part, this game does not offer much in the way of a challenge unless on the very hardest of difficulties.
On the other hand, it is pleasantly addicting. It's fairly relaxing to play, and it's nice to watch you progress towards victory. Tetris may be harrowing at times, but this really isn't. Which can be a good thing if that's what you want. It's a nice simpler alternative to Tetris with plenty of replay value, which is probably the best thing you can say about this game.
So what does this game specifically give you? Plenty, actually. By far the best addition is four player support. If you have many friends who like this game, this version is undoubtedly the best for you. There are also tons of new modes. In the end though, they're just extras. They don't radically change the gameplay and, except for four player support, don't seem to add a ton to the game.
If you like Dr. Mario and own no other version, than this is the one to get.