Yes, I think that the key difference between Angel(us) and Spike is the way their character's were presented. Angel(us) was clear and consistent - Angelus was an entirely seperate character from Angel, not just in their actions, but in their personalities, mannerisms and even dress sense. Angel isn't held accountable for anything Angelus did, because in effect they were different people (though of course he still went for redemption anyway).
Spike was completely different. He was presented as one character. Pre-soul Spike was not presented like Angelus was. Angelus was an inhuman, evil monster. Spike was evil, sure, but was established as an unusual vampire, capable of love and affection, and doing good. He was presented as a character much closer to the "Good" side of the Good/Evil spectrum than Angelus was. Then after he got his soul, he still remained essentially the same character. His personality, mannerisms and dress sense remained the same, he was just Spike+guilt. There's a reason he don't usually bother with seperate names for pre-soul and post-soul Spike.
The AR was jarring because it, for that scene, treated Spike as equal to Angelus, and it completely jarred with what had been established up until then. Another poster said that you can't have it both ways, and that's very true. Was Spike an unusually good vampire who started his road to redemption prior to getting a soul, or was he a soulless monster like Angelus who then became good after his soul. Forget that scene being demeaning to Buffy's character or whatnot, it was simply inconsistent with the Spike that had been established.
People do not excuse Spike for his pre-soul actions so easily because he was not in the same position as Angel(us). Angel and Angelus were two distinct identities, you could file all Angelus' deeds under his name, and all Angel's deeds under his. Spike was just one character the whole way through, everything that he's ever done is lumped all together and you have to take it all. That's the difference.
To answer the thread question, no, it didn't change my opinion. I already hated Spike and Spuffy, it already disgusted me on multiple levels. It was Smashed that changed my opinion, I was actually quite ready to enjoy it before that episode.