We all know Dr. Mario for his various appearances and references e.g. He had a game called Dr.Mario, He was playable in Melee and the Viruses appeared as enemies in Mario and Luigi: Dream Team. One of his games was A little bit of.. Dr. Mario for the DSi Shop/Nintendo Eshop. the game is good because it retains the original Dr. Mario formula while adding some new modes in too. Also, you can change the speed of the pills falling, the level and the music. I will always love the Fever music from that game.
Sadly, the game doesn't have that many modes and it lacks an local/online multiplayer feature which was present in the WiiWare version of Dr. Mario. Without these modes, I fully question if this game is worth the 500 points/£4.50 price tag it was given.
Overall if you are looking to kill time and you like Dr. Mario, then this is the game to do it on.