While there are things I like about Gallery 5, after using it for a couple of weeks, I consider it a significant step backward from Gallery 4.
My site is gallery-driven, and the most popular feature on the site were the global albums. Now that these have been removed, this renders the Gallery rather useless on my site. I have no clue why global albums were removed, but this was a significant site-changer for me.
The featured images feature is a nice thought, but it is very poorly implemented in my opinion. The pictures are cropped to the point of being unrecognizable. The slider is pretty good, though.
I also don't like the "large" viewing option in the gallery. In gallery 4, large-viewing was a lot better looking. In gallery 5 it causes unnecessary scrolling.
I do like some aspects of Gallery 5. But overall, it is far inferior to gallery 4 and previous galleries.
I bought the Maxx dark skin a couple of days ago, and I am very impressed with it. Wish I had knows Ajouz was releasing the light version, as I would have bought that instead! May still buy it when I have the extra cash. Anyway, I highly recommend this skin. Ajouz provides excellent, timely support - and he really listens to his customers. This impresses me tremendously.