Plant me firmly in the biased camp. I love the Astro system. I believe I need it. I might not have kept Ike around without it. Not that Ike is a run-off, or a self-hunter, he isn't, it's just that I'm still a (relatively) in-experienced dog handler, and up to that point every dog I had hunted behind had been (relatively) closer working dogs, or younger dogs that hadn't yet found their range.
Early on I was running the Tri-Tronics G2 collar with the remote-activated beeper. Every 30 seconds I found myself polling the beeper for clues to Ike's location. Hunts were not enjoyable. I was certain that someday I'd lose him, or find him expired on a country road. There was no trust, and I didn't know how to develop trust with a dog like Ike.
The Astro changed all that.
I felt like I could discern between a wide cast or a deer chase. It took some time to grow the trust, and there were some moments that found me dropping my vest and gun to chase after him when he pushed beyond the Astro's range (chasing deer). But I think today we've struck out a mutually beneficial deal: I let him do what he does, and he maintains his manners with minimal tomfoolery. In that regard, the original DC20 did what I needed it to do. But there were opportunities to excel and as such Garmin just released their third iteration with some significant improvements.
The key is that these improvements directly addressed feedback from users of earlier models. For example, the nylon collar on both of my DC30's are frayed and worn. As such they have been replaced with the more popular coated nylon collars that e-collar manufacturers use. Sometimes I have experienced issues charging collars, especially if the collar and the charger are cold. Now they have switched to use a method that offers more direct mating of electrical contacts. I've muddied up the contacts and put both in the freezer over-night, no charging problems at all.
I managed to run the dogs for the first time with a DC40 this weekend. Works as advertised. I can't image the market for a niche product like this is very big, so kudos to Garmin for listening to users' concerns.