The eye-candy highlight of this app is what is commonly referred to as "pinch peek," a gesture-supported feature that lets you pinch-zoom to peek into the photo stacks/albums. It's more than just a simple peek, though. It's a full-on effect (one that you'll probably want to show off to Froyo-less friends). You can see what I'm talking about in the quick video demo below.
In addition to "pinch peek," images also seem to look better in the 3D gallery (said to be 24-bit color) and the app itself runs a little faster and smoother than the Sense gallery. You can also share and/or delete entire albums at once, which I like.
What I like even better is that you can get Froyo's stock 3D gallery app on your EVO.