Power from usb

I'm working on a project that will always be connected to a computer through a powered USB port. Is there any good reason to run that 5v through a regulator or can I just use it as is? I'm running an atmega 328 and some other assorted stepper driver chips. (Stepper power is from a separate source)

Thanks.

USB can power the arduino boards, but is generally unsuccessful in powering any type of motor/servo or larger relays and such. You generally need an external power supply for devices that are large electrical loads.

I'm not worried about usb having enough wattage. All I'm trying to do is power logic. I just wasn't sure if it is good practice to directly tap the 5v from the USB without some on board regulation.

landru: I'm not worried about usb having enough wattage. All I'm trying to do is power logic. I just wasn't sure if it is good practice to directly tap the 5v from the USB without some on board regulation.

USB power is already regulated +5vdc in the PC. There is a 500ma max current limit protected by a on board polyfuse.

Lefty

As stated, USB is technically a regulated voltage.

Aside from that, you generally cannot take an input voltage, regulate it, and achieve the same output voltage. Some voltage drop must be accounted for by the regulator.