I haven't played the original IWBTG, but I found this game is pretty fun and pretty pretty. I really like challenging games. There's something extremely satisfying about beating them and figuring them out, even though they can be frustrating at times. I got to the green apple wave pattern on Beginner (so about 2:10) and 0:53.816 on Normal (I keep touching the boss) so far. I played a while without recording since the start of the second pattern (the part where the bullets that spell "I Wanna Give Up!" explode) lags quite a lot on my computer (though I later realized it didn't matter whether I was recording or not. I need a new CPU).
I'll be commenting mostly on Normal. The first pattern is very hard to get; I spent a good ten minutes on it; good thing it's the first pattern so you can retry it easily. Once you learn it, though, you can do it very consistently. The second pattern is pretty and also doable once you get into the flow (I think the lagging made it a lot harder than it is). I actually found that timing your first movements to the music kind of helps. Generally the game is very learnable, which is a good thing. The patterns after that I only saw on Beginner. The wave pattern was very overwhelming the first time I saw it; I managed to figure out where to stand after a few tries, but I died right after that.
At some point I triggered a soft-lock in the game (see the video). I was playing on Beginner difficulty and I cleared the mid-boss; it flew into the air, like it usually does, but the background didn't change and the game did not progress to the next section. That was the only bug I got, though (I played for about one and a half hour).