I think stinglikeabee and techhelpbb have covered what you need to look for.
As they said, this is a quickly evolving technology. I got my printer 7 months ago. Since then, I can think of at least 6 different materials that have been released. I knew I didn't want to lock myself into a single material. I wanted something that gave me options. There have also been many printers released since I received mine.
I have been running a
Makergear M2 since last April and it has done very well for me. I purchased the kit version ($1475.00) and it was very easy to assemble. I had it up and running in about 6 hours. The hardware itself is very robust. Linear slides on the X and Y axis and a lead screw with guides on the Z axis. My only complaint so far is that the Z axis end stop is tricky to adjust. Once it was set, I haven't had a problem with it.
The hot-end is rated for temperatures up to 230 degrees C so it can print PLA and ABS and uses the same mount that many RepRaps use so it is possible to use third party hot-ends. I have purchased an all-metal hot-end from E3D which will allow me to print nylon, polycarbonate, and many other exotic materials (with proper ventilation). Makergear is also in the process of developing their own all-metal hot-end and dual extruders.
Support through email and the Makergear Google group seems to be very prompt, although I have not needed it yet. Their website can be lacking at times.
On the software side, I use Simplify3D to do the slicing of the .STL files (exported from Inventor) and generate the gcode. It also works with the open source software packages such as slic3r and pronterface. While there are default settings for the slicing, it is worth it to tweak them to see what each setting does. Some settings need to be adjusted depending on what you are printing.