Higher Than Hope is *really* good; I might even rank it second on the album. I'd take Romanticide and The Siren over Planet Hell and Wish I Had an Angel. Kuolema is also good, even though it's a step down from Forever Yours, in my opinion. I have a soft spot for Dead Gardens, although I'd agree it's one of the weaker entries on the album.
Creek Mary's Blood has good parts and not-so-good parts, and definitely overstays its welcome.
This reminds me that Once is a pretty difficult album to rank and evaluate for me. It doesn't have many tracks that stand out as Nightwish favorites to me. Really just Ghost Love Score, Higher Than Hope and Dark Chest of Wonders. It's also in between my favorite and third favorite Nightwish albums, both of which I prefer to it. But whenever I listen to it, I enjoy pretty much everything, and often find myself thinking, "Why don't I listen to this more or think about this song more? This is really good." I don't know, I guess I have a strange attitude to it.