The group I'm currently playing with wanted to use some of the rules from combat and tactics(and spells & magic). Can't say I'm overly enthused, but I'm giving it a go. Primarily we're just using Knockdowns and Critical Hits. Thus far it's rarely been an issue, since nobody has rolled well enough to use them, or the monsters have been effectively immune.
Having said all this, there are a few things I see right off. By and large, there are two many rolls. I think I might get rid of the save vs. PPDM used to resist the knockdown. Either that or I might just change the Knockdown from a random roll, to just the save with a modifier based on the weapon vs. size.