Here's my experience -- shooting Speed Graphic with flash bulbs is a real fun experience. Any D-cells in the Graflite holder will work fine. The Number 5 (or equivelent) will be just as bright as they were "in the old days" if they go off. They'll either work or not, but I've had 99% of my NOS bulbs work just fine. I've never had one explode but I suppose the stories persist becuase it has happened in the past. I wouldn't lick a bulb... I don't know why anyone would.
One thing to remember that hasn't been mentioned yet is that when you use bulbs you must be using "M" synch, not X.
Also know that the efficiency of the flash is related to the shutter speed - about 100% of the guide number can be expected at 1/30 second, but less at 1/125, etc. This is because at 1/30 the shutter will be open for the full duration of the flash burn, but at faster speeds the shutter will be open for only a part of the flash burn. In the 1970-era Kodak Professional Photoguides are a really great dial calculator that has these efficiency factors built into the dial.
Here's an example of the "power loss" due to shutter speed (#5 bulb and M sych):
.9 efficiency at 1/25, 1/30
.8 @ 1/50, 1/60
.7 @ 1/100, 1/125
.6 @ 1/200, 1/250
.4 @ 1/400, 1/500