I love this level: it's mostly very pretty, it's large, it offers a real sense of discovery because it's just confusing enough to keep you running around for a while without getting boringly repetitive. I still haven't quite finished it, but that's mostly because I want to save a part of it for later. :-)
There's a few, well, I suppose they're SGEs? Like, for example, when the red keyhole blocks disappear, behind them there's a tile (or just the background, possibly) that's a different colour from all the surrounding tiles. But, nothing very serious.