How has my Evade House Rule worked in actual play?
Short answer? Well.
It essentially boils down to paying 1 extra movement point and making an unopposed DX roll against a friendly, or paying 1 extra movement point and making an opposed DX roll against a hostile. Or a concerned friend, I suppose.
It's worked out very well.
Too often in the past, PCs would essentially form a combat line and then have their second, third, fourth rankers just walk through each other like they weren't there. Even invisible friends who were concentrating on a spell and had touch-based magical defenses on them were evaded with total ease. You just got right by and did your thing. You could easily down a foe in front of you, and then step back, and have your friend step up and take your spot - or the friend step through stationary you with a Committed Attack and attack someone else. All on a one-second time scale where your buddy is a tiny fraction of a second slower than you. Bleh. It felt stupid. So stupid, in fact, that if the back guys did it the players would groan about how it wasn't realistic that that guy could do that, not this turn anyway.
Instead, the addition of the DX roll - penalized for big friends - has helped immensely. It's rarely missed, but it does mean the clumsy sorts or risk-averse aren't keen to move through occupied hexes.
The additional cost means a hallway of friends actually slows you down, which by the rules as written it does not . . . not at all. That also means rushing foes don't always get to just fill in a gap, either, with a back ranker . . . but well-coordinated foes often can, which makes for an interesting differentiation between enemies.
The one addition I've made is that you need a roll to detect an invisible friend - Hearing-2, penalized for combat noise - to attempt to avoid them unless you're certain where they are (it happens), or they hear you and move out of your way.
All in all, it's added a lot of versimilitude and interesting tactical choices to combat without any real addition to the rules, just an expansion of two basic concepts - Evade, and the Bad Footing extra cost of movement when your footing is poor or limited.