The thing that makes bokeh so "zen" or esoteric seeming is that in human vision, it's very difficult to observe the out of focus areas because we naturally focus when we look at that so it really is very abstract. Only a trained high priest could observe something that elusive.

But in photography it can create very obvious and measurable effects which are really no mystery at all. All the more noticeable since it is something that we don't notice in normal vision so is a kind of special quality of photographs versus paintings, illustrations or normal vision. So I think it really is very important and not esoteric at all.

In my non-expert observation there are two or three qualities for bokeh:

1. Octagonal type highlights versus round. Octagonal might be interesting for certain effects but I'd generally consider it crappy. If you have the next two right, it's not very noticeable. Manufacturers will try to pass off curved aperture blades as "good bokeh" and this is really a minor part of it.

2. Smoothness of low contrast backgrounds (a factor of #3 below). This just means that out-of-focus background or foreground elements will be extra soft and smooth. For low contrast conditions without harsh highlights, this isn't so different among lenses and seems to be a very subtle subjective thing but if you throw in harsh high contrast point sources of light, you will get surreal rings or octagonal shapes. If it's moderate contrast, they will overlap and not be obvious but will give a subtle graininess to the background.

3. Evenness of out-of-focus highlights.

The donut/rolled-condom look with emphasized edges is pretty bad.

Totally smooth discs edge to center would be OK but still include harsh unnatural edges at the outside of the circle. This looks like a bunch of translucent coins floating in the air.

Soft edged blobs, gradually more intense in the center like a sphere are most natural and soft looking although technically the even, sharp edged flat disc described above is more "perfect" from an engineering standpoint. Designing a lens for this soft effect in the background means that foreground elements will have the reverse effect and look like donuts but normally foreground elements out of focus are avoided from a compositional standpoint. There are special defocus control lenses available though few bother with this extreme of engineering.

Links

google image search for bokeh

nice technical description

nice illustrative article

comparison of 50mm bokeh for Nikon

bokeh comparisons for quite a few lenses

Perfect computer simulated bokeh

esoteric history of the term in English

long drawn out coverage of the topic

shows a way to chart bokeh curves

Good Bokeh Lense List
Unfortunately most are real expensive though there is the theory that only lenses with uncorrected spherical abberation are able to create soft bokeh.

Leica, Zeiss & Minolta, generally.

180mm f/2.8 AI(S) and AF Nikkors*

Carl Zeis Luna Sonnar 135MM F4 for Contax Rangefinder or Hasselblad
Soft but polygonal highlights. Possible to get adapters to mount to an SLR and inexpensive, like $200 used.

135mm f/2 DC AF-D Nikkor*

Nikkor 135 f/2.8 AIS MF $320 new $100 used
reportedly not a good lens at all wide open.

Nikkor 105mm f/2.5 AI-S
supposed to be awesome $340 new, cheap used. Lightweight.

105mm f/1.8 AI(S) Nikkor

105mm f/2 DC AF-D Nikkor*

100/2

100mm f/2.8 Nikon Series E

Nikkor 85mm f/1.4 AF-D & AI(S)
Tamron 90mm macro

(Nikkor 85mm f/1.8)

85 f/2.0

Leica Summilux 50mm f/1.4 $2000

Nikon 50 mm f2.0 AI
old model with the long barrel reported excellent bokeh

Nikon 50mm f/1.2 (manual focus $430 gray market new, $150 used)
soft at the edges for that price.

50/1.7

Nikon 35 mm f2.8 shift
reported best 35mm bokeh, fixed aperture is odd and might not mount.

Nikkor-O 35 mm f/2 AF [non-AI, AI]
good and
bad examples, opinions mixed. Useful for closeups also, $300 new.

Nikkor 35mm f/1.2 ($$!!)

28/2 AF or The 20 mm f3.5 AIS
Supposed to be quite nice but have to get very close to get anything out of focus.

28 f/2.8

24 f/2.8

Nikon 35-70mm f2.8 AF
nice but almost lifelessly smooth bokeh.

24-85mm f3.5-4.5 AF-S G
"bright, contrasty, fast focusing, great coverage, and has good out of focus treatment throughout it's range"

75-150mm f/3.5 Nikon Series E*