Sadly, there's no multiplayer with Dr. Mario Express. There is a scoreboard, but it's local scores only. Furthermore, you don't have the option to take on a friend in Versus. Had Nintendo included this option, there's no doubt that this would've been an absolute must-download for every DSi owner. Without it, it may seem a little shallow for some players, even for a $5 game.
Nevertheless, if you're a fan of puzzle games and want to treat your DSi (and yourself) to something fun for both quick and lengthy sessions, Dr. Mario Express is worth the prescription.