A couple of years ago, I was interested in a kit lens replacement for my A100. They were clearing out some old Minolta lenses, so I checked out the 24-105 and 24-85. Both lenses seemed to be pretty good, but didn't quite "grab" me enough to part with the cash. I liked the 24mm angle -- just wide enough on APS-C for most use, IMHO. It's been a while, but these are my vague recollections from trying the lenses out in the store and "chimping". The 24-105 was good, but the 24-85 was sharper and faster. It seemed to focus and snap the photo faster, although I wasn't sure what aspect of the lens made it seem that way. The larger range of the 24-105 was tempting, though. The one thing that was odd about the 24-85, I had read about online -- sure enough, the bokeh was a bit strange. The 24-105 had smoother bokeh, but the 24-85 would get some patterns in it that could be distracting to some. Overall, the 24-85 seemed to me the better lens. I wouldn't call the 24-105 "soft", but it didn't seem as sharp as I would have liked.
When I discovered that the store also had a Tamron 17-50/2.8, I tried that, and was blown away -- faster, sharper, etc., so I never looked back at those Minolta models.
Going forward, I have occasionally bought cheap old lenses, so I decided to try the 28-105xi. (With a very slight mark on the edge of the front element, it was priced at only $19!) What I see from the performance of this lens sounded similar to other comments I've seen about the 28-105 lenses. In good light, this is a pretty good lens. It has surprised me. In poor light, it's pretty awful. It's particularly bad at the wide end. But recently I discovered that at f8, even my 28mm shots looked really nice -- all the resolution I could want, and great color. The 105mm end doesn't need to be stopped down as much, I don't think, before it looks good. Wide open, somewhere in the range, it has the "dreamy" look someone mentioned. I guess it could make for interesting portraits, but I was kind of surprised to see it show up! Overall, the color looks great, and the bokeh is decent. (You aren't going to get nice round highlights, particularly as you don't want to use the lens wide-open anyway, but with the angular geometric shapes, I kind of like the effect, and it doesn't seem to have otherwise distracting backgrounds like you sometimes see with "bad bokeh". But I can see where many others might not grade the bokeh as high as I do with this lens.)
I really like the 28-105 range for some situations, and if it were a 24-105, I'd probably be a bit happier. 16-105 sounds much better, but that lens has gotten some lackluster reviews, but maybe I should revisit that one someday. But for $19, I think I'd prefer the 28-105 over the others.