I backed the original Maslow and also the Maslow 4, and recently a 4.1 upgrade. The creator is a really dedicated guy and the Maslow is a great CNC for those who cut sheets goods from wood (though folks have adapted it to other materials) and are OK with some tinkering.
There is a decent sized community that supports the software as well.
I don't have direct experience with long, straight cuts in my use case, but based on what I have seen in the forums the Maslow 4 is pretty good at them. It has an auto-calibration feature that the original did not have which makes it much less finicky to dial in than the original Maslow.
In the forums, I have seen people cutting cabinet parts with it, so I have to assume the straightness is acceptable, but it might be worth asking those who are using it for that purpose specifically.
There is a decent sized community that supports the software as well.