I like my LC4896. I got it used for 1/6 the asking price of a new one. I pushed my gantry to see if it flexed like you said and the whole gantry moved parallel. It did not skew at all.
One of the cool things about the unit is the x and z axis screws and nuts are covered at all time along with the linear bearings. As a result they stay very clean. I have never needed to clean or relube them since I bought the machine.
One thing I would call a detraction would be the toolpath preview and drive software. You cannot view the toolpath at the same time you move the gantry. I wish techno would make a plugin for mach 3 so we could use that. I have even contemplated replacing the controller to run geckos just so I can use mach 3.