We've had Simmentals for over 20 years. Started with the "original" blond and white spotted cows. Great milking cows, but that type took too long to feed out, so the feedlots didn't like them as well as a more moderate breed. Now they're moderate framed and meaty, similar to a lot of the present day breeds really.
The ones I've had have always been docile, they've done well at the feed lot (we've run three groups through Ranch to Rail) and have good weight gains. A lot of the more modern bloodlines are polled, and of course most are either red or black now.
They also cross really really good with Brahmans!