From what I can see, it seems very costly when/if your forum gets big, and seems limited in the features, ie. the maximum of 750 users online. Although it's a lot, the cost you have to pay for that far supersedes the cost of buying hosting independently and a full license.
I have an IP.Board license, and hosting, so I may be subjective about it though, but it seems to be of more value, in that you can use the license at any time and not be budgeted on a certain time frame before you have to pay again, or your forum will be removed.