TokiSora is my favorite H!P single of ALL TIME. It's just that good. I imagine myself listening to it forever.
This is the exception rather than the norm though, I prefer upbeat songs, and the rest of my top 10 (heck my top 30) is full of upbeat music. (I consider I WISH a snore-fest )
With all that said I really liked Yuugure, loved its dance most of all. I can listen to this several times, but I prefer Seishun kozou by a wide margin (which is a really cool song!)