Initial D Arcade Stage + Burnout + Chase HQ = Drift City
Is this game good? Yes, but you should never go into playing a MMO like the game is going to be a perfect game, every MMO has it's downsides. The racing is solid, I barely lag living in Australia. The missions are fun, when you get to lv24 you'll be required to level up more to get missions accessible. That's about the only grind to this game.
The chases are fast and exciting and when you have a party, an element of strategy is applied. Having your party ambush the enemies (HUV) can be devilishly fun.
There's 40 cars available at the current time (September '07), including the AE86 Trueno, Smart Fortwo, MR-S, Saturn Sky and so on. As the game is updated more cars will be released. Upgrading is not available yet, however in future you will be able to upgrade stage 1 cars through to the final stage.
What are the downsides? The usual MMO suspects; Spammers in global chat, Cliché Takumi / AE86 players (Honestly, you'll see them a lot) and so on.
If you like driving games, this game will probably capture your attention. I'm personally not into cars, but this game has me hooked. Check it out, it's worth your time.