I have the same issue as the OP: Digispark enumerates fine with keyboard example and for programming (albeit after flashing to firmware version 1.06) but not with the DigiUSB example. Dmesg:
[ 2240.100140] usb 5-2: new low-speed USB device number 39 using uhci_hcd
[ 2240.280163] usb 5-2: device descriptor read/64, error -71
[ 2240.616047] usb 5-2: new low-speed USB device number 40 using uhci_hcd
[ 2240.736144] usb 5-2: device descriptor read/64, error -71
[ 2241.016158] usb 5-2: device descriptor read/64, error -71
[ 2241.232069] usb 5-2: new low-speed USB device number 41 using uhci_hcd
[ 2241.644133] usb 5-2: device not accepting address 41, error -71
[ 2241.756059] usb 5-2: new low-speed USB device number 42 using uhci_hcd
[ 2242.164143] usb 5-2: device not accepting address 42, error -71
[ 2242.164168] hub 5-0:1.0: unable to enumerate USB device on port 2
I opened up libraries/DigisparkUSB/DigiUSB.cpp and in 'void DigiUSBDevice::begin()' changed '_delay_ms(1)' to '_delay_ms(10)'.
Reflashed into the Digispark and the DigiUSB example works!