There is a lot of online debate about whether the issues with multiplayer are lag or cheaters. I don't care which it is: multiplayer is terrible. Unfortunately, just of your rewardable achievements are going to be through multiplayer, which is impossibly inconsistent. The regular races mostly work fine. They are single player against bots. Those achievements are possible. So 2/2 stars for those races, 0/2 stars for multiplayer, and 0/1 star for the amount of free content.