It's pretty great - it has nice tooling and well structured problems to sharpen your programming skill on. One issue I discovered is, if you are studying a less popular language, the difficulty ratings tend to be inaccurate - things that are labeled medium might be super easy, while things labeled easy might be super difficult.

Also, just because something passes in your local doesn't mean it will pass on exercism - the resources allocated to their cloud servers are skinnier than what you are likely running. This is part of what pushes problems another level up in difficulty.