I just got my Acer A500 and have problems accessing the it's storage from my ubuntu machines.
If I try it with Win7 in VirtualBox it is automatically mounted without requiring any actions on the tablet itself.
Ubuntu accepts the USB device (it can be passed to vbox) but nothing further. The only dmesg entry is:
[119174.117100] usb 1-1.2: new high speed USB device using ehci_hcd and address 22
I'm able to mount and use other usb storage devices.