> Why should we measure medical technology at the rate of new drugs developed?

Well, I'd stand behind the assertion that it is a reasonable approximation to our ability to understand and modify a biological system. But, I'll happily concede that this is not the only game in town. Your point about tissue engineering is well made, this is highly exciting and should provide some real benefits. But there is a awful lot of hard biology to master here; so while I really hope that we see some rapid initial progress, long term exponential growth here is going to be just as difficult as it is elsewhere in biology.