DISCLAIMER: my transmission is one of those freak unicorns, it won't even go out of neutral if it's cold. It'll slip occasionally until it warms up. I've got the trans-go shift kit in it, along with two and a half bottles of Lucas and the trans file has been tuned... It's actually pretty impressive how many "bandaids" have been thrown at the damn thing.
There's still some hard shifts every once in a while, and it without a doubt needs a full rebuild, but I'm slowly stockpiling parts to build it into a "performance" trans. It'll hold until I have everything, but if I hadn't done anything, it would be undriveable by now.