ShwanNot sure how I did however it was fun as hell to co-cast; and a great game to watch.
I thought your casting was good. There were two big things though: You seemed to have not been around TF2 for a while? (I think you mentioned this) as at a couple of points you kinda explained things or treated them as newish when they were pretty well accepted strats. (Sorry that I can't remember the example I had.) Second was talking about what happened a bit too long. A couple time it was awkward because Slin wanted to start doing the play by play of a push out of last or a midfight but you were still talking about a previous round or play. At one point he cut you off which was probably the right move by Slin but kinda hurts the dynamic between you.
Looking at that paragraph it looks like I hated your cast but I really did enjoy it. Obviously only being given a hour or two of warning to do a cast means that you couldn't really fully prepare for it and I think that made it kinda hard.
Generally for casts, both for tf.tv and the larger tf2 and esports community there will be a play by play person telling what where and who and a analyst person who explains why teams are doing what they are, what teams should be doing, how they are going wrong etc... You mentioned to Slin at the end how you let him handle the play by play, which is good because he is good at doing that. You did a good job of talking about why teams were doing what they were but you probably should work on that for the future (again you did have little notice and I definitely couldn't do better.
Hopefully you cast more in the future! :D