I never considered Safari to be much of a contender as far as web browsers go. At least until version 5 was released. The Safari extension ecosystem is building up nicely. Macworld has compiled a list of 25 that are worth checking out.
Get 25 great Safari extensions | Browsers & Add-Ons | MacUser | Macworld
Get 25 great Safari extensions | Browsers & Add-Ons | MacUser | Macworld