It wasn't too busy and I can highly recommend taking a tour with one of the guides. Usually I like to explore on my own but the guide was very knowledgeable. 

The museum is quite nice as well and shows the history and need for reliable time instruments through the ages. And especially the need for accurate time for navigation.

New Atmos clocks start at € 6.550 - US$ 6,600 - £5,550 so a bit pricey for aspiring clock enthusiasts.  However, you can find pre-owned clocks in good shape and serviced for $1000 or less on eBay so that's much more reasonable. 

Does anyone have any experience with these clocks or have any tips for finding a good used one? Most desirable models? Year range?

These ones with the round clock face seem to be the most common on the used market.

I recently watched this video which pretty much explains everything about how it works. Simple but fascinating at the same time.

More information from JLC: http://www.jaeger-lecoultre.com/eu/en/watches/atmos.html

Word origin:

“hōra” from Greek, meaning hour or time in English.
"o" interfix
“-logy" is a suffix in the English language, meaning ‘the study of”

Horology: the study of time

Definition of Horology

according to a reputable English and American dictionary:

Oxford English Dictionary

• The study and measurement of time.
• The art of making clocks and watches.

Merriam-Webster

• the science of measuring time
• the art of making instruments for indicating time

Translations (using Google Translate)

French: horlogerie
Spanish: horología
Italian: orologeria
Japanese:  Horojī (ホロジー)
German: Uhrmacherkunst (clock maker art)

Instruments to measure time

Some examples of instruments that measure time are clocks, watches, clockwork, sundials, hourglasses, clepsydras, timers, time recorders, marine chronometers and atomic clocks