I've never stayed at the Hyatt Madeleine (prefer the location of the Grand or the Scribe) so can't comment on the rooms.
The location, however, is very, very good -- just a few steps from boutiques in the Madeleine/St Honoré area, and no more than a 5-minute walk to the Printemps and Galleries Lafayette department stores. Unlike the Hilton (I agree -- Hilton's location is awful unless you want to stare at the Eiffel Tower for 4 days), the Hyatt is in an area chock-full of shops and restaurants.
Places to check out near the Hyatt: In the Madeleine, Fauchon for incredible take-out food. Between Madeleine and Opéra on rue Vignon, La Ferme St-Hubert for the most unbelieveable grilled ham and cheese sandwich (called a croque-monsieur) that you will ever, ever have. On rue Tronchet near Madeleine, duck into a tiny shop called La Carpe for some of the most wonderful kitchen gadgets and supplies.
[This message has been edited by wideman (edited 12-11-2000).]