I think Future GI Guy will be the best one to answer your questions. GI is a very procedural field -- they do a lot of upper endoscopies, colonoscopies, sigmoidoscopies, etc. It's largely outpatient-based, but there is a pretty big inpatient component to it as well. Your patient population depends on what you choose to specialize in GI. For example, if you're a liver specialist, you will have a ton of cirrhosis patients, and will probably spend more time in the inpatient setting.
They often work a lot of hours -- especially since the demand for colonoscopies has been greatly increasing. But because they tend to do a lot of procedures, they also get compensated more than many other fields in Internal Medicine.
Now we'll just wait for GI Guy to fill in the details... 🙂