Whoa, 5000 times :O
I'll nerf Platform Arena with the coming release, as most people found it too hard. Not so sure about Spike Pit (after all, it's a trinket challenge, and it was already nerfed) and Narrow Path.
I'll release a second beta with included fourth level soon ("Inversed Floors", bonus points for understanding what kind of challenge it has), and maybe include the real ending. That, or I'll just include the level and nerf.
I think the problem people has with making levels too hard is that they've probably succeed in the main game already, and make the challenges much harder due to that. Because, before, when I just won the game fully, w/all trinkets, etc, I still had problems with the featured levels, but they got easier by the time I play VVVVVV more.
I intended this to be easier, and tried to make it "too easy" for myself (I died 72 times on my first full play on this level, with all the trinkets), but maybe it wasn't enough?
Also, none complained about the spikes in the overworld, so I guess they're OK (I was afraid they would be frustrating).