My situation now: tab doesn't boot into system, doesn't show in adb, doesn't show in flashtool (offline or online), doesn't boot to recovery, doesn't boot to download and doesn't show in windows. There's only one sign of life: when I plug it into a usb cable which is attached to my PC I get the windows "connect sound". And I get the disconnect/connect sounds when turning it off while attached to PC.
I assume that I can throw away my tab. If you know better, don't be afraid to tell me!