I was on law review. It kind of sucked and didn't help my writing at all. It's really not that hard to learn how to do basic citations correctly and that's pretty much all you need in the real world. Being on a journal teaches you nearly every obscure rule you can find in the Bluebook (especially, if you have the displeasure of editing an international piece.) From a substantive perspective, journals focus on academic pieces that are, for the most part, useless theoretical trash. As far as writing skills go, being on a journal might actually make you a worse writer. To become a decent legal writer, your sentences should be short and to the point. Law review articles, by their academic nature, necessitate long-winded run-on sentences.
However, being on a journal does look great on a resume and proves to employers you aren't scared of tedious work that is of little importance. Also, although the work sucked, I really did enjoy getting to know the other people on law review. Like any horrific experience, you bond with those around you who are going through the same thing. Most people had a great sense of humor. It probably won't hurt to know these people later on in my professional career either.
You also experience a certain sense of satisfaction when you finish editing a piece and correcting every mistake. There's something comforting in the methodical nature of the editing process even if the end result ultimately doesn't matter. I compare it to the inverse of sand mandalas created by Buddhist monks. They spend all this time making these beautiful mandalas and then ritualistically destroy them as a testament to the impermanence of life. Conversely, we spend all this time polishing these academic turds that will live their useless life for ever as a testament to the never-ending drudgery of life as an attorney.