That being said, I understand exactly why they've done it. For one, they're a business and they want to make money. Best way to make money is to provide services that your customers want and are willing to pay for. If Blizzard can figure out how to code the transition to change achievements that are faction specific, mounts that are faction specific, reputations, etc. then go for it, whatever. I don't have to change factions, it's entirely optional.
I can see the appeal, though. I have a tauren hunter by the name of Poloma. She used to be called Baress and was my first main. I moved her when free server transfers opened up for her server months and months ago. Opalandra the druid may have been my very first toon ever, but Baress/Poloma was the one I leveled. I made it to level 20 before the trial I had downloaded expired and got her to just over 40 before quitting the game for a bit to study abroad in Italy, and since then have gotten her to 56. She's hanging out in Winterspring, sitting on 300 skinning because I'm too lazy to take her to Northrend (dumb, I know). Mining is her other profession, for gold, but it's really low level, only around 110.
I was the true huntard so long ago, even carrying some gear with Strength on it (oh, the horror!) and probably had never laid a trap in my entire existance. I still find the hunter class very complex to master: easiest to level and get into, hardest to master, truely. The faction change would benefit her most, I think. I've gotten rid of the pure strength gear (yeah, burned that stuff fast, man it was bad... well... except for her gloves and pants... they still had agility and I was tired of spending gold...), upgraded what I could without breaking the bank seeing as Outland is so close, and gotten her rested up. I don't play her often, though, because of her server.
Know how I said that I moved her during a free transfer period? Well, I didn't read the fine print. Turns out she was moved to a new Latin American server. I wouldn't care too much, except my Spanish is terrible and I have no hope at all with Portuguese. I feel like the dumb American tourist intruding on their space, and I hate it. It makes playing not so fun. I have options, though, especially with the upcoming faction switch.
As much as I dislike the idea, as much as I despise the concept of transforming her into something she's not, the fact that I could change her into a dwarf or a Draenei and move her to Emerald Dream or some such appeals to me. She has hours of work put into her, pets that I fell in love with (my first pet is a wolf from Mulgore named Karo) and she's whethered all the hunter changes throughout. She's from pre-BC for goodness sakes, just like Opal. She deserves a second chance.
There is another option, of course. One that may appeal even more, simply because it would require a great deal less work, and I could do it today, if I wanted. I could delete my orc hunter on Gul'dan and bring her over. I've thought about doing this hundreds of times. It would get rid of the whole "I don't speak Spanish well enough to play here" problem I'm having with Quel'Thalas (the server, not the zone, of course) and would get her on a server with my level 80. She'd have gold and a bank alt to send stuff to, and everything.
I haven't done it, yet. I haven't taken the plunge. It's on my mind, though. I'd hate to just ignore Poloma forever. Like Opal, she deserves better.