We made the trip from Cody to Old Faithful in a few hours one day. It was worth the drive.
*Old Faithful is fun to watch. It gradually bubbles and steams to an erruption that lasts a long enough to get some good pics. The geyeser is surrounded by a large walkway. Along that walkway you can see a lot of small geyesers, bubbling pools, springs and mini "prismatic" springs. When we arrived, Old Faithful was going off approximately every 90 minutes. When you arrive, find a park ranger and ask them when it will next go off. They'll provide a 20 minute window of when it will go off. This way you can check out the interpretive buildings (there are 2 that we saw), or enjoy a walk around the walkway. There are benches to sit and watch the eruption.
*Hiking paths: there are other walkways and hiking paths that take you farther away from Old Faithful. They look like they would be fun to do, but we opted not to do it because it was so hot when we visited and my parents (in their 60s and some physical limitations) would have tired out.
*Water bottle filling stations: Free, filtered, treated water. A must and much appreciated if you're visiting during warm weather.
*Gift shop: there are a few, one very, very large one. Lots to choose from.
*Food: Not too sure how many there are but there are two, pick up at the counter and seat yourself type arrangements, and maybe one in the hotel. The food we ordered was pretty good.
*Free entry with park pass.
*parking can be chaotic. There are a few lots and it's pretty confusing once you get there about where to park. There appears to be general confusion amongst people arriving and leaving. Also, when you first get there and park, there appears to be a lack of directions about where you are and where various features are. A large map on with "you are here" would be a great addition.
*food service: When we ordered food at one of the cafeterias and it was crazy! The line was long, no biggie, but waiting for orders was ridiculous. They had a teeny, tiny area for people to wait for their numbers to be called. We stood there for half an hour waiting for our number. Crazy when all we ordered was a few pre-made sandwiches, pre-packaged fruit and veggie trays and one order of chicken strips and fries and one hamburger and fries. Customers were hot (it was uncomfortably warm in there) and, understandably, cranky for the long wait, cramped waiting area, heat and what seemed to be repeated mistakes in orders creating more delays. We'd watch someone wait forever for their order, only to go back up to the counter and ask for things missing, or mistakes with orders. It was a bit pricey - $6 just for a burger and that was their 'special'. No fries included. To anyone else going there for the day, I would definitly recommend not eating here, or bringing your own lunch. Not worth the delay when there is so much to see in Yellow Stone. It might be different if you are at the hotel and there is a restaurant, or maybe we hit the cafeteria on a bad day, but it definitly put a bit of a damper on our visit.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.