What are the disadvantages of teaching graphing skills using micro-computer based laboratories?
This will be of necessity a personal answer, based on many years' teaching experience. I found that graphing skills needed to be built up gradually and in a very structured way if students were to actually understand what they were doing. Many of them never really grasped anything more complex than a bar chart, because it was assumed that they could jump easily from that to a curve which shows the relationship between two quantities. In fact this step involves quite a conceptual jump, and if its significance is underestimated, graphs remain something which 'decorates' their experiments instead of informing their learning.
If you are to become good at graphs you need to actually draw them, and allowing a microcomputer to do it for you cheats you of this necessary experience. The value of microcomputer based labs is to generate a lot of data in a short time and to represent that data graphically without delay. It's fantastic if you already understand graphs, but not much use for establishing that learning.
The other major drawback is that you have to understand the limitations of the software which draws the graph, which is an extra layer of learning. (For instance, will it draw a line of best fit, or just join the dots? Do the students know which is appropriate when?)