The 200mm L is on my short list as well.
At $800 and it being a black lens, it's a lot more low-key than the 'big white lens' -- it's supposed to be REALLY sharp.
To be specific, you mean the 200mm f/2.8L II. "200 L" could also refer to the 200mm f/2L IS - which is not black, not low-key, definitely no where near $800, but is really REALLY sharp.
The 200/2.8L II is a very nice lens - I had one for a while, which I sold after getting the 70-200mm f/2.8L
IS II. One thing to note is that you need a fair bit of light to handhold a non-IS lens at 200mm, especially on a crop body.
Weird; for L cash I'd have expected they were all sealed :/
It depends on the design and intended use of a lens. Its not practical, for example, to seal a push-pull design, but it was popular a several years ago. Same for a TS_E lens. Any lens that extends while zooming or focusing is impractical to seal, but the design keeps weight and cost down. Some of the older designs were around before sealing became popular, so there are lots of choices.
If you need weather sealing, be sure to select a lens with that feature. Having a choice can be a good thing.
It also depends on the design date, I think. A push-pull design isn't a problem - the 28-300mm f/3.5-5.6L has a push-pull design similar to the 100-400mm, but the 28-300mm is weather-sealed. Extending zooms like the 24-105mm and 24-70mm are weather-sealed, too.
Canon started offering 'dust- and weather-resistant' lenses in late 1999. Before that, the white primes and zooms did have weather sealing under the switches and focus/zoom rings (so the 100-400mm, 400/5.6L, 300/4L IS, etc. all have some degree of sealing) - what's lacking is seal at the mount gasket.
L primes after 2006 are also weather-sealed - so, the 85mm f/1.2L II from 2006 is not, whereas the 50mm f/1.2L (released in 2007) is, as are the 14mm f/2.8L II, the 24mm f/2.8L II, and the 100mm f/2.8L Macro IS.