The part I disagreed with:

The only drawback of Balsamiq Mockups is that you run the risk of getting a little cutesy. Everything in it is of this “sketch” style, which might get old after a while.

This is actually something I particularly like about Balsamiq – the “handwritten” informal look of the lines & letters says something about the fidelity of the mockup. I remember reading a UX blog post that resonated with me (can’t find it now, will keep looking) which recommended using overlapping lines for edges to indicate that the screen shouldn’t be taken as a final design but something needing input and refinement. The hand drawn buttons / text / edges in Balsmiq convey this pretty nicely.