I hit level 49 on my warrior last night, so down to single digits until Outland. It actually makes me a little sad as I've really enjoyed what Blizzard has done with the old starting zones so far. Every zone I've been in so far has been very engaging and interesting.
I finished up Badlands (the questing line in there involving Black Dragonflight eggs is really fantastic) and have moved on to Searing Gorge. That's the first place that I seem to have found a little bit of repeat from what I remember before, but it's still all pretty well done.
The only downside that I've been able to find from the new smooth questing paths from 1-60 and the fact that Blizzard has removed all the hopping back and forth between continents is that getting training for new spells and abilities has become a bit more challenging as there is really no reason whatsoever to go back to a capital city other than that. So it's no longer just a matter of "I'll swing by and grab that on my next zeppelin trip" because there isn't going to be a next zeppelin trip.
So, that's been a bit of a struggle, but not a big deal overall.
My guild is basically one day away from hitting level 20, which will open up the BoA head pieces, which should accelerate my leveling even further. Right now I'm at 1 day, 2 hours played time to level 49, which seems absolutely lightning fast to me. I know Joana's old record for 1-60 was 4 days, 20 hours which was absolultely breathtaking speed at the time. And it looks like I'm going to completely blow that away. Of course, Joana wasn't working with 35% BoA xp bonuses and a 10% guild xp bonus, so that makes a big difference. However, even if you adjust for that 45% boost, it should still come out to somewhere around 2 days, 16 hours to 60, and it at least looks like I'm going to be faster than that.
The difference would at least seem to be driven by the improvements that Blizzard has made to the questing experience.