1.) He is my favorite fictional character. I particularly like the combination of genius and vulnerability and I think it's never been played better than by B.C.
2.) "We're not a couple!" "Yes, you are"... Was Irene right? Yes and no. They act like an "old married couple" (and that's where a lot of the humor of the show comes from) and there is obviously a huge amount of mutual trust and liking. But I am sure that there is no sexual or romantic side to their relationship. John is desperately trying to find a girl-friend. Sherlock thinks romance and desire are "dangerous" and "destructive", so if he was attracted to men (or just to John), he would not feel comfortable around him and certainly would not want to live with him. John is clearly bothered by other people's misconception of their friendship, while Sherlock seems to find it at most slightly amusing. Poor Irene, I'm sure she never had a real friend. The only human connection she knows about is sex, so of course she'd think that any two people who are close would be sleeping with each other.
3.) No. Frankly, I don't much care. Maybe Irene got that part right when she told him the higher power he believed in was himself.
4.) Never seen any other. Had a crush on SH since I read the stories as a teenager and don't like literary adaptations in general. I did not want my image of the great detective spoiled. I only agreed to watch "Sherlock" originally because somebody told me Martin Freeman was in it and I had really admired his performance in "The Office". I was never more pleasantly surprised...
5.) In many ways, BBC's modern Sherlock is an improvement on the Conan Doyle character. He's not quite so invincible, more flawed, more interesting, more complex. Also, the original is clearly a "good man" and a hero, while in this version he is still struggling with these issues. We meet him at an earlier stage in his development. I expect that, if the show continues, the creators will make Sherlock become more and more like the literary Holmes. Pity, really... Although I would like to see that weird tenderness evolve that Holmes shows in the stories sometimes. I am sure the actor could pull that off really well. It'd be difficult, though, to show Holmes lulling Watson to sleep with his violin on TV without making the "I want them to be in love" people go totally berserk.