I find the software very intuitive and easy to experiment with. They provide an assortment of templates, but it is very easy to create a new flow chart from scratch, by drawing a starting shape and using connector lines. If you are already familiar with designing powerpoint diagrams, the concept is similar, except with Visio, it is much more effortless to align objects, and the software will automatically expand your figure onto another page if necessary.
The product defaults to blue shaded boxes which are difficult to read and not very printer-friendly. I have to manually fix it every time. The other limitation is that when you want to save Visio or transfer your image into a different program (i.e., going into a powerpoint presentation), the image doesn't always transfer in exactly the way because it may appear slightly differently. I also wish there were more icons available, so I could use them as objects in presentations. There is a way to modify them, but there is a rather limited selection, since the diagrams were intended to be used for business or work purposes (not as a general database of copyright free clip art).
I would highly recommend using Visio if you like to create interesting flow charts and plan to do so on a regular basis.
I was a bit of a skeptic when my vice-chair highly recommended Visio for designing algorithms and flow-charts. I initially used it reluctantly, but I was able to figure out how to make fairly appealing flow charts within minutes. This makes for much more interesting presentations and hand-outs. Most people who have seen my Visio flowcharts have been impressed. The completed flow charts would take significantly longer to create in powerpoint or other software programs.