Try these links to get some basics on the different levels of properties/service styles that are offered:

Hyatt's Corporate website gives a few details on this link:

http://www.hyatt.com/corporate/hyatt/gateway.jhtml

Of course the Hotel Review link is a great option for reviews of the Hyatt Hotels (unofficial), which I think was put together by either one of the moderators here, or a dedicated FT member:

http://www.hotelreview.de.vu/


Another good source for reviews is Trip Advisor, though not dedicated soley to Hyatt, but many hotels, places of interest, cities, people, etc.

http://www.tripadvisor.com/