I see lots of divided opinions on the self bailing deck. One thing I should mention is that the 18' Silver Streak is actually 20' overall with the swallow tail. It is a big boat for an 18', so the self bailing deck doesn't seem like such an over the top feature. I rarely go out with more than 3 people, usually just 2 so there won't be that much added weight in the back. I do like the idea of the plugs just in case. The only drawback I see besides the cost is that I will lose 5" of freeboard.
I have always had trouble with bilge pumps in the past. They seem to be prone to problems. It would be nice to not have to rely on one. Plus I agree that no matter how good you think you cleaned the boat, the bilge water always manages to rot, and stink it up.