About stagnating knowledge though - I used ramdisk solutions for a good few years on Windows because of the poor cold start times for certain programs and obviously it had an enormous benefit. I doubt I would have thought of that if I hadn't spent a while using Amigas (not saying that ramdisks are/were unique to Amigas btw).
Personally I think in say a systems admin role it's incredibly useful for someone to have had some sort of cross-platform experience. It gets people to think of solutions that aren't so ordinary, and also it helps point out flaws in a different platform much more obviously (rather than accepting the walls one lives in when using only one platform). I don't think it matters greatly whether the 'other platform' one has used is a considerably older one, though the line has to be drawn somewhere.
Admittedly I've been wondering along a similar line about stagnating knowledge, when I think of what I learnt from NT4 that has benefited me in terms of troubleshooting problems affecting later versions of Windows, even though it's not as if what I experienced in terms of problems with NT4 SP4 can be directly applied to say the next service pack for Win7.
