I'm going to make a some broad-brush generalizations here, but they are consistant with my observations. Your mileage may vary. These observations seem to apply to most templates and jigs.
At best, templates and jigs provide great repeatability and accuracy, once you have them properly set up / tuned. The amount of setup required can vary from jig to jig but all involve a level of upfront investment of time to accomplish this. This applies to dovetail jigs, the Incra (and other) fences when used for highly precise cuts, as well as templates themselves. Once the setup is complete (or template made), if properly designed and used they can save a lot of time and reduce the amount of firewood generated.
Take for example, a trivel design I'm using to hone my Incra skills (first page attached, free download from Incra.com). Making the body of the trivet simply involves 56 cuts lowering the wood over a spinning bit and sliding the wood between two depth stops. The upfront time is spent in setting the fence to cut precisely in the center of the wood and placing the depth stops for each end such that the two intersecting bits meet precisely at the same point. It may just be my shortage of skill but I've twice spent an hour or so tuning the stops and only have it within about 1/16" in a couple of places. After the second (last) adjustment though, I was able to cut 6 trivet bases (336 cuts across 4 different bits) in a bit over an hour. Once I get the final setup, a "production run" would be a breeze.
To a much lesser extent but the same is true with the 4 dovetail drawers I made for my shop. I spent most of an hour on the setup and about 5 minutes per drawer making the cuts. If it'd been a kitchen full of drawers, the time would have been very time effective for me (not yet having the skill for hand-cut).
Fortunately for me, the slight depth stop error on the trivets only showes up on the perimeter so I've been able to trim off the perimeter and end up with some pretty spectacular 4"x4" 3-D coasters made from Maple and Padauk, minimizing the firewood pile.
Anyway, I've found that with precisely sized square and flat stock and a properly set up jig, these cuts are relatively easy but they do not come without some investment of time up front. Since my mission is building my skills rather than production, I'm intentionally choosing projects that require different skills than those I used in my last projects. This puts me low on the learning curve, requiring a disproportionate amount of setup compared to others that have used these tools for an extensive period of time (like others here), but my point remains. There's an up front investment of your time.
Any one who approaches making dovetailed drawers (possibly other than in an assembly line, with previously set up equipment) expecting the speed and ease of "glue and screw" joints is misled.
Good jigs and templates can help minimize making firewood from your prime wood, but they don't come without investment of time. Bad ones... well, I won't even go there...
Just my $0.04... (just like $0.02, but twice as long!)
<Edit> Hmm.. maybe I should have made that $0.06!!
