I just did a clutch, new axles, flywheel today on my red car... and it made me think about this. Putting the trans on yourself can be a bitch... but if you have the trans, it doesn't take that long to put it on and start the car... you could just put in like four bolts and it would be alright.
Lance brings up a good point about safety and the flywheel. I know its a small chance that it would pop off, but if it did it could kill or hurt someone. I think a couple extra minutes is worth the peace of mind.