My general experience with my knights is that they can be effective in the round they charge but in the following turns they are really not achieving much. This also means that if they get charged they are usually screwed. Well, they have some good staying power but they will almost never beat an enemy unless they get serious help. In my opinion this is purely due to that they kill very few enemies at S3.
I have been thinking about building a 12 knight unit with great weapons. In 7th edition rules you did not benefit from +2S when on horse back, but that has changed in the 8th edition rules. So they will loose 1+ Sv for 2+ Sv, but I think that the benefit of being S5 will make a difference. I am not concerned of ASL as at I3 thay will usually strike last anyway.
I am not really looking for advice here, I will build the unit anyway for the fun of it, but I was wondering if anyone tried it out in the field and what the experience is?