Glyph's rundown of it is really great, IMO. I pretty much swear by Karmagen. We actually use the RC version-we play so little that we tend to use the old attribute costs anyway(plus, we use the more old school slimmer Karma awards on top of it, so it pretty much balances out the progression.) Given that we only get to play a few times a year, quick progression is the least on our minds, and starting with a more robust character is pretty perfect for us. I just love how it's easier to get those low skills you want to round out your characters. (We do play slightly higher than average power games. I can't say they're elite or anything, but we do like a cut above average.)
That said, if I were to make some houserules for Karmagen myself, it would be somewhat like the German errata, but with some twists.
-Metas cost BP in Karma, keeping this.
-I'd either, however:
Method A: leave the x3 cost into play, as the RC, OR...
Method B: I'd increase it to x5, BUT have everyone buy stats from 1-6 as per normal and then add on extras. x5 cost with the bigger stats does get far too expensive, IMO. Plus it sorta ends up favoring some races over others.
If I want a strong Street Sam(despite Strength being a dumpstat

), I can just roll up Bob the Ork, take a reasonable Strength and cyber it up the rest of the way rather than pay enormous amounts for the 9. x3 cost with everyone starting from 1-6 is a bit TOO cheap, but I think with the x5 that works pretty well. Not sure which route I'd take. Under x3, right now it costs a regular troll 107 Karma to get to Body 9. Under the x5, start from 1 rule, it would cost him 70. So its cheaper, but the troll would ALSO have to purchase up the attributes they take a minus to on top of it. So if x3 Attribute Cost Troll wanted a 9 Body and 3 Charisma(maybe he backs up socially), it would cost 107+15 or 122 Karma. If the same troll took the same attributes in the x5 Variant, it would cost 70+70, or 140 Karma. He'd actually be more expensive the second way, but not by much. My only fear with this is that it would push some characters back into 'archetypes' too much, which is actually something I like to avoid(I actually think stuff like troll faces and ork mages are made of win, and I'd fear this method would start to stifle that a bit. ) Still, it has some benefits. Currently, as it is now, with ''Start at high bases with x5'', it shoves it way too far in the other direction.
-Remove Magic/Resonance/Edge from the limit. Human Mages and Technos end up running into problems here in my experience. At least I'd take Magic or Resonance out of the half Karma limit.
-If using x3 cost, keep the cost of Knowledge and Language skills. That x3 cost is pretty relaxed. If x5 cost, I'd give Intuition+Logicx5 in free Knowledge skill Karma(to be purchased as Karma. So 7 Karma for a 3 rating, for example.) A 3 Logic and 4 Intuition would net 35 Karma, which is a decent little boost; it would enable, if someone wanted an average spread of knowledge/language, 5 skills at rating 3 each. More or less if they wanted to have a lot of low skills or a few higher. Extra would have to come from the bulk Karma pool as per normal.
I'm sold on a lot of this, except for what I think the more ideal attribute spread is. In any case I'd keep it with 750 Karma as the base, and just let the ''less or more'' happen from table to table, depending on what people wanted for their game.