Product review (2 stars): Lasted less than 4 years
Here is my original review, but please see the updates, below:

So my circa 1991 Viking Pro oven was taking forever to get hot, and then it didn't really get hot enough. After internet research, I determined the common cause was ignitor failure. Ordered from Home Appliance Parts and paid less than $50. Arrived in about 2 weeks. Extremely well packaged ... original Viking box triple wrapped in bubblewrap, then placed in a sturdy and size appropriate box for shipping. Kudos for wrapping.

Installation was mostly easy. (I always worry about "fits all ranges," and usually fits nothing I have.) Remove oven racks. Remove side shelves that hold oven racks. Remove bottom tray from oven. All the above simply lift out without tools. Old ignitor right there in front of me and removed with a phillips head screwdriver (two screws). Old unit and new unit, physically look 100% the same, except ... New unit has two male electrical connectors, old unit has one male and one female, as does oven. Old unit had male/female connectors spliced onto unit to adapt it to the oven, so I removed the female spliced connector from the old unit and spliced it onto the new unit. Now, new unit has one male, one female connector. Connectors slide into place. Assemble in reverse. Oven lights off instantly and immediately heats, just like it should. Took less than 15 minutes, start to finish, even with the wire splicing.

Tip: I assume that some ovens are set up to accept an ignitor with two male ends (as the ignitor was shipped), and some are probably like mine with alternate connections. Consider purchasing separately (in advance), crimp style or ceramic connectors so that when everything is torn apart, you don't have to put it back together again while you go and search out correct wire connectors for the electrical side.

UPDATE:  Amazon prices have gone way up! Although I paid less than $40 on Amazon last year, as of this writing Amazon is over $100.

UPDATE: 2/9/17. The OEM failed after less than 4 years. In the meantime, OEM prices have gone over $100, while aftermarket prices are about $17 on the big auction website, so I have replaced the OEM with aftermarket. If you choose to go with aftermarket, I have found there are two styles. One is a round, barber pole style of ignitor and the other is a flat style. When I previously bought the barber style, they were so fragile that two were broken in shipment, so I only buy the flat aftermarket style now.