That said, designers often over-worry about logos initially. If you put enough marketing power behind it and the company is still on a growth curve, the logo will eventually become associated with the brand and it wont matter whether it was obviously a 'U', a Chinese coin or a ghost ;)
EDIT: The question now is, is uber on such a growth curve that they can still get away with this. My gut says 'no,' but only time will tell.
Does it look clean, professional and trustworthy? You have decent vector images of it? No negative associations? Just run with it, there's better things designer time can be spent on.
I think there's two reasons for changing it afterwards. It is starting to clash with the visual design of the site around it, and needs some touch-ups, or your company is moulting, and shedding it's past skin.