Yo Jimbo!
Homedistiller, IMO, is only a pain because of the amount of info and the various running commentaries that are about the aspects of the hobby. Yes of course, some feel that it's not as welcoming because there's a few of those who display a "redneck" attitude toward newer members. They have no understanding about why it is that the smart still is popular here (hell a lot of "them" have never seen one). The feeling here is that it's more "English" (do I mean civilised? sort of, but not in a way that's disrespectful of the people over at HD - they have a wealth of stuff that I'm very appreciative of).
I'd think that as long as you have the server space, then if possible the main site is well worth keeping.
Just because the aspects of what we're doing is a very narrow, equipment specific part of it. So while the main site would grow/change etc at a slower rate, as it's dependant on how much time you (and we) have to write and/or contribute articles and any other stuff we find/link.
Yes, it is nice the have a refresh and/or redesign every now and again, it's sort of up to you matey, they're "your" forums/site.
The search suggestion is a goody, but as the questions/answers build up it still tends to end up with a core of X number of questions that are repeatedly asked and answered. A lot of people with just look at the first couple of threads in the given topic and if they don't see something that answers their Q, then they just post...... It could be that you\'d have to do some sort of stats search so we can work out what the most commonly asked question is, then a tutorial could be written, with pictures if necessary. I for one, have written a couple of tutorials about some other aspects of home brewing/winemaking. I could easily do something like that, but of course, I can\'t really do that to a deadline as my work interferes with my life too much as it is. So possible, yes, when, well, when it\'s done......
Me, I've been hanging around here for a good while, as you know. So it's hardly surprising that I keep coming back, but still in a "friend you haven't seen for a couple of weeks" sort of way. Ha! I can't really use the site when I'm working because I only have a web capable smartphone/PDA with me. So if anyones got any good excuses for me to use, to convince "erindoors" that I need a 3G laptop....... all ideas/suggestions gratefully appreciated ;-P
Now as for software possibilities, I prefer vBulletin. It's pretty damn good. Cost etc ? don't know. just that there's a number of forums that I know of or post at who use it to great success.

Sticky threads at the top of certain topics would help the searcher who only looks into a couple of posts then asks the same question again and again.