Last week one my primary occupation was wireframing. It took me quite a long time to finish the first wireframes using a normal vector graphics editor and I started to look after a simpler and more efficient way to create my mockups. I quickly stumbled over Balsamiq Mockups.
So, if you need to do wireframes from time to time, Balsamiq Mockups is probably the right tool for you. If you do wireframes and nothing but wireframes all day long, you probably better stay with the tool you're already using.
With US$ 79 it's quite pricey, and I personally think that's too expensive. But if you need it, you'll pay.