We've been using Workgroup PDM - and before that, PDMworks - for years. But not continuously, only on big collaborative projects. Every time we dive into it again, it's so excruciatingly complicated and confusing that I regularly lose work and have to repeat it. Once, when a client asked for more parts that I'd designed and put into PDM, I brought up my local copies by accident and had them built. I forgot that the local copies weren't up to date, so I had to rebuild the parts, costing us money. PDM has been an absolute minefield.
By contrast, we occasionally use Subversion to track changes on collaborative work. Subversion is much, much easier to learn than PDM, it's quite intuitive, and I can go back to it after months away without much of a relearning curve. It also lets more than one person work on an assembly at once, just resolving any differences when the work goes back into the repository, and this can be a big advantage.
Does anyone have extensive experience with both Subversion (or anything similar) and PDM, and if so can you spell out why PDM is any better? I sure can't see it.