timppu: Depends on the RTS. If the game lets me freely slow down the gameplay speed any time I want (e.g. Starcraft), I don't really feel rushed, even if the particular mission was about having to e.g. build up defenses fast for the incoming enemy, or destroy the enemy in a given time.

Then there were games like Warcraft 3 which didn't let me freely change the game speed... ack.

I think the main thing that interests me in RTS games is the Lego syndrome, ie. first building up something, and then you get to smash it down. Or even better, you can keep your own Lego castle intact, and go smash your friend's castle to bits. This urge to build up/smash down is encoded into every male's genetic code.

Hence I prefer base-building and resource-gathering RTS games, to the RTS games where you have only certain number of units. I generally disliked the Starcraft special missions where you didn't have a base and couldn't produce more units.