perspiration == effectiveness?

I work out on the rowing machine twice per
week, among other things; running, stationary
bike, swimming, tennis, squash. It's the best
full body workout I know. I typically do 25 min.,
250 calories.

However, there's one odd thing - I hardly
sweat! Is this a bad sign? Is the 'fitness
feeling' an illusion, am I really not getting my
money's worth? As opposed to the bike,
where I'm drenched.

Also, squash generates the most perspiration.
Which seems weird, because it doesn't feel
so draining as the others.

--
Rich