If you like Metroidvanias, you'll love Saira. If you hate Metroidvanias, you'll love that Saira doesn't actually feel like a Metroidvania.
You'll love Saira if you have a pulse, basically. And $8.99 to spare. And Steam.
I briefly lauded Nifflas' most recent exploration/platformer/puzzler in my 2009 indie game roundup, but it bears repeating: Saira is one of the most atmospheric, engaging, and varied exploration-based platformers ever. If you have any interest in games like Metroid, Myst, or Nifflas' classic Knytt series, you'd be doing yourself a disservice not to check it out (especially at this price).