That's why I maxed the RAM, put a 400MHz Sonnet in, replaced the hard drive with a CF card, and popped in Ethernet and USB to make it useful. I agree, when new, it wouldn't have been impressive compared to the rest of the Mac range, as far as performance goes, and to make them hum wouldn't have been cheap back in the day. But I did all of the above for under $100, so that was money well spent.
And I'm not worried about parts commonality between the Powerbooks and the TAM, just means I have a plentiful supply of spares.
