Which model did you try?

Alot of the open source ones are built by the user so they're bound to be a little DIY-ish
They need to be properly calibrated and maintained too so if it wasn't performing well it was most likely user error rather than the machine itself.

I've just had some models 3d-printed by someone who owns an UP! 3d printer and the quality and accuracy is superb, definatly still want one