I think Dumbo is rather lame...but I know when my kids were little they adored all those types of rides. What Dumbo has that others don't is the mystique and the magic..it's Dumbo...and it's the classic MK ride so even grownups ride it and smile

I love that they are doing twin Dumbos...that makes the ride more exciting. And that circus themed waiting line sounds like so much fun. We've done Dumbo once and have no real interest in doing it again (my kids are 9 and 10) - but will definitely do the new twin Dumbos because it sounds different.
As for Sppedway, my DS9 still loves that ride. But he also loves all the antique car rides at all the other amusement parks we go to. From my perspective, I'm disappointed they don't make the Speedway a little more attractive to adults. I actually really enjoy all the antique car rides at other parks. They're usually cool and shady and it's fun to be driven along by your kids.
I find on speedway, the pedal is really hard to push, the lineup area is awfully designed (HOT), loading and unloading is slow, and the track itself is so-so.
It could be done SO much better- still keeping along the same theme of kids driving but with stuff to make it more attractive and interesting to adults. A Cars theme would be fun or even interesting things to see along the route, SHADE, etc.