I am also a pastry chef, my restaurant/bakery specializes in cakes and home-style desserts. I love to harvest ideas for flavor combinations and presentation when we visit Disney (or anywhere else, for that matter).
Yep, Signatures definitely have the best presentation. The desserts are usually as tasty as you'd expect them to be, based on how lovely they look. I love the Banana White Chocolate Toffee Tower at Brown Derby, that fab Almond Cheesecake at Narcoosee's (even though I usually don't like cheesecake), and the pithivier at the patisserie in France. Anything from the Karamel Kuche is great too.
A few misses for me:
I haven't had a Disney cupcake that I thought was yummy. The frosting is traditional Amerian "buttercream": globs of whipped shortening and powdered sugar.
In their credit, the cake is usually moist.
The creme brulee at the France patisserie - watery texture and almost no flavor. Every other creme brulee I've had in Disney has been good though.
That horrendous key lime glop in a cup at Flametree BBQ - ugh.
I also LOVE bread pudding, have won awards for mine, and try it nearly everywhere I go (unless it has raisins). The bread pudding at Ohana is hit or miss - I really loved it the first time I tried it, but the second time it was dried out and just wasn't wonderful. I've had some at various buffets around Disney and it's usually quite good.
Have fun tasting all the fun sweet stuff Disney has to offer!