Tim, we are planning on upgrading to either 2.4 or 2.5 this summer. In your experience was it completely necessary to install and utilize memchache?
Couple of questions I'd really love to here about:
1. Is your memcache node a separate server... specs, single node?
2. Are you running apache or nginx with php-fpm?
3. Do you have a general sense of 2.5 readiness?
It sounds like you're probably live already, but If you are interested I have a jmeter script to simulate quiz taking which we used when we were thinking about upgrading to 2.4 earlier this year. It can simulate answering most of the quiz types out there and I'd like to get it out to the community if others are interested.
I didn't see any improvement for quizzes at that time, but maybe with memcache there would be gains.