Good? Or bad? Difficult to say. Indeed quite some people reach the forum because they have some problems (technical, payment, spam, developer stuff, …). And slowing growth could mean less bugs in Skype. On the other hand the concurrent users online isn’t growing that fast anymore, so this could be another reason.
Not all visitors come to the forum with problems: there are also some interesting discussions going on on wanted features, evolution of Skype, competing products, contests, etc.
There are subsections in other languages (Japanese, Italian, German and Spanish). Although i know that not everybody speaks English, i somehow deplore that there are subsections. It has always been allowed to post in your own language on the forum, so why create subsections? It is probably easier for the forum moderators.
The red dots (and curve) represents the mean new usernames per day on a monthly basis. In May 2007 (last month) 337 new users were added per day. There were some higher peaks (in January almost 400 new users per day).
Conclusion: Forum users are still increasing, although, in my opinion there is a clear slowdown, probably due to the slower growth of Skype users.