It would have been interesting to have continued having them. Especially since they were actually a minor power in the galaxy (they were only on one planet that was uninhabitable) and they wouldn't have been friends. Lets not forget that they weren't convinced to turn off the wraith engine jammer, even with the knowledge it causes stargates to explode (they didn't use them, so they didn't care how many would die because of it).
Sadly I can't call it a missed opportunity. We probably would have seen them again, but the series got cancelled. Thats the missed opportunity.