I really loved it! Seeing the alternate time lines was amazing! Seeing Celestia leading like a General was epic, especially considering it's hard to see her in that light. Also, I didn't notice it when I watched it but DrWolf pointed out Rainbow Dash having an prosthetic wing was a really cool and nice touch. I always wondered with what seemingly seems to be very bare bones medicine what help a Pegasus that lost their wing would get.
Also, were the CMC in this? I didn't see them, but it would be sure interesting. Also, not sure if an error or not but I thought only Chrysalis could speak but the others couldn't? Yet you hear one speak disguised as Rainbow Dash speak. I did love this episode but I agree with others that I felt her reasoning for hating CM was pretty weak.