Are you just starting out or do you have quite a bit of reloading 'under your belt', already?
While it may not be the right choice for many (who probably shoot a lot more than I do -- currently about a flat a week) I am very happy I chose to stick with a single stage press and I purchased a MEC Junior.
I am able to change adjustments to accomodate my constant 'experimenting' and trying / changing various components, etc. (This turns out to be a pretty major factor in reloading 28's).
One primary reason I started reloading in the first palce was to force myself to stop working when I got home (and thus save not only my health but probably my marriage, too!) so, I enjoy reloading for the sake of it.
I'm confident everything I am learning now by trying so many variations (especially in the 28 ga) is going to serve me well if and when I do decide to go with a progressive . . .
On the other hand, if you are:
a) sure you know the recipe and component combo you're going to settle on;
b) going to shoot a lot, and
c) are not planning on trying a lot of different components,
a progressive may be the way to go, for you!