1. The attendant is responsible for putting the berth up and down. They should ask you what time you'd like it put down early in the evening or tell you to ring for them when you are ready. They go off duty about 10 pm and you should ask for a time before then. They will typically put the room in day mode while you are at breakfast. I usually leave the door and curtain open and pull the call button on leaving for breakfast. If the attendant is either unavailable to make up the room or dictates the time ("I will put the beds down at 7 if you want me to do it") I will not tip them at all as this is the most fundamental part of their job. The roomette lower is tricky, it is a spring loaded steel frame that you have simultaneously push the pedal with your foot while pulling on the end with your hand. While I've never got a finger caught in one, it seems more than possible.
2. The showers in the Metropolitan Lounge are very nice. If you want a shower the day you leave Chicago they are a better option than the one onboard. I always use them changing trains heading west through Chicago, skipping a shower on the inbound train. The Lounge attendant will hold your driver's license as security for the shower key card.
3. There is very limited luggage space in a roomette. Roomettes are really small, about 6' x 3'. The open floorspace when the berth is down and the door closed is an about 18" x 6" space by the door. An airline carry on should fit under the seat but could be hard to dig out. I put my bag on the common rack downstairs.
4. The "temperature" control only controls the electric floor heat, when it controls anything. My experience is it only does anything about 50% if the time. Cooling is provided by the car's HVAC system through the vent in the ceiling over the door. The amount of airflow can be controlled by louvers if they're not broken.
5. There is only one outlet. If you need to plug more thing in at a time, you'll need a power strip or something similar. Be sure and get one with a conventional straight-in plug. The angled plugs that are common now will not work in some roomettes where the outlet is recessed.

Finally the Cardinal is a New York-Washington-Chicago train that runs three days a week. The other Eastern overnight trains serving Chicago are the daily New York Lake Shore Limited from New York and the daily Capitol Limited (soon to become the Floridian) from Washington.