It's been almost exactly six years since I bought my first 3D printer. In that time I've owned three 3D printers, all of which still work, and two of which I still own and use fairly constantly.
To date all of my printers have been fully-built models from the Chinese manufacturer TierTime. I've decided that it's time to take the next step and build my own printer.
With my six years of experience 3D printing, I think it's fair to call myself at least a highly competent journeyman. But I'm already learning that the open source world does some things very differently from what I'm used to in TierTime's products.
For example, TierTime's slicer provides only a handful of print settings: layer height, infill, print quality (one of three options), whether you want a raft, and a few parameters for the amount of support material. Slic3r Prusa Edition has around 65 different print settings, not counting the ones under the "Advanced" menu. This clearly represents not just a steeper learning curve, but an entirely different philosophy of how 3D printing should work from the user perspective. While I can see the value of the extra control, I've also managed to get by just fine so far with one tenth the number of parameters to adjust.
Another big, and surprising, difference is how the RepRap world still seems to be struggling with support and rafts. Six years ago, the Up's break-away supports were a major point in their favor (and one of the reasons I didn't go with something like a Makerbot back in 2011). While it's not always perfect, the support material I print with my current printers is generally fairly easy to remove, and the resulting surface of the print after the support is removed usually ranges from pretty good to perfect. But from reading online discussion, it seems that a lot of people still struggle with getting their printers to print supports that are easy to remove and don't leave ugly surfaces behind. I expected the open source community would have figured this out by now--and it's disappointing because not having reliable support and rafts really does limit what you can print and how you can print it.
On the other hand, the limited controls TierTime has given me for the materials (I can only set the extruder and bed temperature on my Up, vs. 15 different material parameters in Slic3r) has limited some of my printing options. I haven't been able to get some interesting filaments (like flexible filament) to work well, or even at all. And being able to print with four different plastics in a single print, as the multi-material upgrade allows, will be a real treat. Even if one of those materials winds up being soluble support because of the problems with break-away supports.
I'm sure I've only just begun to scratch the surface. Being an experienced 3D printer taking my first steps into the world of open source printers is guaranteed to be an interesting adventure.