I'm probably just the man you are looking for... I too am SBC and have served as the pastor of a General Baptist (General Assocaiton of General Baptists) church. If you are looking at another of the General Baptist sects, some of my comments may not be pertinent.
A couple of observations from serving as both pastor (5 years) and associational moderator (3 years).
First, the people were God's people. Nice in the way church people are nice. In the GBC, they tended toward social awkwardness and were seemingly a decade or more behind current social trends, dress, worldview, etc. I found this to be true even at the national level in the GBC, but that may not be a bad thing... Depends on your own perspective!
Second, I found that they were theologically and doctrinally "shallow." That does not mean "uninformed" but it does mean that they lacked a wide exposure to the way others thought about certain theological or doctrinal issues. Many, or even most, had not been exposed to any other thought than what was taught in their church(s) and they really were not very interested in finding out, either. At the national level, their leaders were reasonably well trained, but they too had the "folksy" attitude rather than the more serious attitude that often goes along with SBC national figures. I suspect that comes from a much smaller denomination, where the entire denomination is smaller than one or two of the largest SBC churches, but I have nothing quantitative to back up that opinion.
Third, they are indeed "general" in their doctrine, and this was perhaps the thing that caused the most work for me. With their fully-fledged doctrine that one can or could loose their salvation if they were not "prayed up" there was a steady stream of work to do with congregants who thought that they "did something" sinful (or worse, when they started staying away from church, you knew that they had some reason wrapped around a sin they did not want to confess). They were also very staunch about "whosoever will" even to the extent of being categorized as holding "easy believism." That was more individual than denomination wide, with different people holding different levels of that doctrine.
Fourth, there was a lot of talk about "preaching the gospel" but not much action to back that up. They mostly gathered to themselves and did not much deal with "the world" outside the church. The attitude was along the lines of, "If those people out there in the world would get right with God, they would come in here and join us." When I laid plans to enter the neighborhood in an evangelistic sense, they balked and found reasons to not do that sort of work. We managed to get out a few times, but it was always difficult. They much preferred the lunch after...
The particular little church I led had seen their last new member almost 20 years before I arrived (yes, their only new member was 20 years ago!). I added several families, cleaned out the baptistery, and started doing outreach, weddings, etc. As soon as new families came into the church and wanted a say in the business meetings, the "this is my church" thing started up pretty quickly. While they liked the money and attendance (hands to do the work) that came with new blood, they did not like the idea that "the Pastor could add a few families and have his way with our church." That was the beginning of the end for me.
Fifth, they do some things differently than the SBC, especially in church polity. In the GB, pastors and deacons are "credentialed" by a presbytery, made up of the pastors and deacons of sister churches in the association. If you did not meet their criteria, they would not credential you, and I did not, with an SBC ordination, so I never ended up as a credentialed pastor, or a member of the church I led for 5 years. When they elected me as moderator over the association they had to figure out a way to handle that, seeing as how I wasn't credentialed, so they made a new category for me to accommodate me, seeing as how I was the one willing to do the work. They have a lot of business meetings, which I found very similar to SBC church meetings overall, save that they seldom had much in the way of business to accomplish. They also direct support missionaries, so we were expected to get on board with deputation campaigns and visits from missionaries when they were in town.
Otherwise, it was mostly church as usual, and other than keeping in mind their "general" theology, we got along well. I taught SS and preached every service. I did some of my most Calvinistic sermons while I was there, and one was for the annual meeting of the association, which had the entire assembly standing and shouting praise to God. It was sort of fun to lead them to a deeper understanding of God's sovereignty and to challenge some of their shallowly held doctrines, but I always had to bear in mind that I was the interloper, not one of their own. I've since returned to the SBC, but the thought has crossed my mind of reuniting with the GB because they have open pulpits all over and are a people that need leadership. God would have to say so, however.

raying: