Yeah, I will probably toss out the glitch rules as written. Critical glitches really don't feel good to even consider using. Maiming a character or causing them a loss in a key attribute or totaling a vehicle over a single bad test is way overkill, and falls into the Bad DMing Choice realm for me.
That said, it seems extremely unlikely to ever happen, especially to higher dice pool characters, so you end up punishing people who have low dice pools, which is a bummer as a player to go through. Yeah, you can also Edge your way out of it, and pretty affordably, but that brings me back to the 'what's the point of the rule then' type feeling.
I'd rather have some kind of "drama die" type mechanic. So for example, one special die you roll with each test. If it comes up a 1, reroll it. If it still comes up a 1, you have a complication. On a 6, rerolled to be a hit, you have something good happen instead. More like a Glitch Die idea, rather than the unlikely scenario of a total wipeout on a dice pool. Then its not so much about a skill flub, and more about random chance events in combat and creating opportunities for interesting story ideas you can throw in. Save the real drama for a failed test + a complication and there's your 'fumble' effect if you want to play it that way.