Hey Cbuttre835,
I am one of those guys who never minded changing dies - as long as it was for metallic cartridge presses. I have a L&L progressive press and do not bother using their bushing system. I just don't mind changing metallic dies. It's no big deal to me.
Shotshell reloading, on the other hand, is a very different thing. It's not just the MEC 650 that is a real pain to change dies; it is all MECs and every other brand and type of shotshell press that is just way too much to change as other folks have already stated earlier. Some folks that use the Pacific/Hornady 366 progressive press will purchase a complete head unit in other guages, and it can be changed out with the removal and replacement of a few bolts. You also have to change out shell plates and tweak things a bit. Changing guages on a 366 by changing heads may be OK for some guys, but I really would not even bother doing that.
Multiple presses as other folks have said is the easiest and least frustrating way to go. Until last year when I sold most of my equipment, I had seven shotshell presses and a whole bunch of metallic presses that used to take up all the space on my reloading bench which was 20 feet long. When we moved to our present location in 2005, I built a new reloading bench which was 12 feet long and would never accomodate all my reloading presses.
I solved the problem by cutting two plates of half inch steel (each 12"X16"), bolting each of them to the bench 4 feet in from each end, and then drilling and tapping bolt holes in each steel plate for each press I owned. It really wasn't that many holes considering I had three 366 presses that could all use the same holes, three MEC Sizemasters that all used the same holes, and several RCBS presses that used the same holes. I also made bolt holes for my lubrisizer and casetrimmer in each plate. With my two plates, I could solidly mount any two pieces of equipment and change them out very rapidly. I also made two shelves on an adjacent wall to hold all the presses and equipment that would be used on the steel plates. That way, I could store the equipment in a small space on the storage shelves when not in use, and I would have plenty of room to work on the bench. I did mount one RCBS powder measure on an RCBS stand directly to the bench, but it is the only piece of equipment permantly mounted to the bench.
In the past year and a half, however, I sold over 50 guns and most of my presses and dies. I still like using my steel plates to change the presses I still have, but my equipment storage shelves look mighty empty now.
In any case, consider multiple shotshell presses instead of changing dies. It really is less frustrating. You might also consider steel plates with your own bolt holes if space becomes a problem for you.
Best wishes,
Dave Wile