Let me add to the head count (Lord knows I can't match the volume) on this.
I greatly prefer a mailing list, especially for a topic like TextMate, which is well-defined and comparatively low-traffic. Most of the traffic is interesting. If the topic were something like "DSL service," with its exponential variants of vendor, hardware, locale, usage... then a searchable, hierarchical knowledge base makes sense. This list doesn't come close to those requirements.
I also like it that when I ask a question on a mailing list, the answer itself gets delivered to me. On a forum you essentially have to go through a separate mailing-list subscription process for each thread of interest -- and even then, the mailing contains a link for logging in to read the response, not the response itself. Again, probably useful if the topic isn't focused, but not on a list that can be doubled in volume over the question of whether it should be a list.
It is idle to say a forum generically indicates (to one person) that a vendor provides better support, or that there is a better community. In the real-world case of TextMate, the vendor and community support are excellent. Whether a mailing list "says" to one person's mind that there isn't support, or that the sponsor isn't way-cool, is irrelevant. In the real world, the support is there, and the way-cool goes into the product, not into customizing a forum and prosecuting its innumerable bugs.
Foregoing excellent product support, or even an excellent product, just because some of that support doesn't come through a web browser, is perverse.
The title of this thread, "Actual Forum," is really pretty patronizing. This mailing list is an effective tool by which a healthy community does in fact communicate, and well. It doesn't need a centralized server to validate it, or make it more "actual."
— F