Pretty much.
Power management and drivers are the weak points for USB instruments.
Computer decides it's time to "be green" and conserve energy? *bam*... instrument just went offline.
Manufacturers make their money on hardware, and provide just enough driver support to make the thing work.
The drivers usually aren't the best in my experience, so there's memory leaks and crashes that happen more often than not.
That said, with a little bit of work you can get USB devices to work for extended periods of time. Depending on the application and mobility requirements, it may be a better solution than PXI or other more reliable alternatives.
