Bill has some good questions. That big, fancy MFD looks great at first. But it goes against the old words of wisdom "Don't keep all of your eggs in one basket". I wouldn't fly one without at least having something like a Garmin 296 which has the instrument panel page.
Without knowing for sure, I'd guess that the repair costs for the MFD would eclipse that of rebuilding an analog instrument. Who will repair the MFD? Will you be forced to deal with only the manufacturer? If you land somewhere away from home and lose one function, you could be leaving your plane there for a long time.
On the other side of things, the MFD is probably much lighter.
