I regularly use and SP5 Micro Spiral mixer, I've had good results with it, but as others have noted, for high hydration doughs - it's usually better to use the double hydration method. I purchased mine from TMB Baking south of San Francisco and they are extremely helpful. Although, it's often reported to be made by "Esmach" it's actually made by Avancini - an Italian cooking equipment manufacturer. I recently had a chance to use a Haussler Alpha spiral mixer. The mixer looks almost identical to the SP5, however, it has a tilting head and a removable bowl. I haven't had that much trouble cleaning the SP5- you just pour some water in and after dissolving any remaining dough, you wipe it out clean. Obviously, because of the tilting head and removable dough - the cleaning process is much more expedient with the Haussler.
What really surprised me, however, is that it typically takes about 5-6 minutes to get good dough cohesion with the SP5. When using the Haussler, the dough cohesion was achieved in less than 4 minutes, which was quite amazing. Of course, the conditions weren't scientifically identical, but I was making Tartine's basic country dough recipes and within 100 miles of the location I typically bake, so certainly substantially similar in terms of climate, ingredients, etc.
If I get a chance, I would like to try making brioche in the Haussler, the Tartine Brioche recipe is quite wet, and I have use the double hydration method with this dough in the SP5. I'm wondering if the Haussler could achieve cohesion without having to use the double hydration method. I haven't measured the revolutions per minute with either machine - so I'm not sure if there is any difference there either.