Like repechage, I, too, had a Bob Jackson (1974ish) that was kind of messed up in the bottom bracket. I ended up having a shop glue a Phil Wood BB in with red Loctite. Worked great until the bike was stolen 15 years later. Once the BB issue was solved, it rode well. It was gorgeous, too, red with white head tube and seat tube panels and white block "Bob Jackson" decals. (Personally, I think those look better than the slanted letter graphics.)

The word was that there was a time - not sure when, but later than the mid-70s - when Jackson retired, the quality suffered, and he came out of retirement to put things to right. No personal knowledge, and I can't even remember where I heard this. But from what I have heard, anything after 2000 - and probably back to 1995 or maybe even 1990 - will be well made and serve you well.