I agree with Barry, not so much with Hal. Far from a gutsy move it was merely the third attempt at replacing him (John and Guy were the earlier attempts). Kyle was less an innovation than an attempt at appealing to a demographic at that point, made all the more pointless because we had a valid successor (John) already.
Basically they fucked up the GL storyline up from the beginning and only made it worse with every attempt at repairing it. By the end, an evil space bug that lived in his ass didn't seem so out of place.
I'm not talking so much about replacing him (btw, Guy was NEVER a replacement), I am talking about actually turning him into a villain.
That was a huge move on DCs part. Never before had an A-list DC character become a supervillain (a mass murdering one at that).