For watching TV shows on the iPad, I have three choices: Netflix, HBO, and ABC. As you might guess, the ABC app only gives me access to ABC shows--there are a lot of them, though. The app gives you access to full episodes of most, if not all, currently or recently running shows, and also lets you view the schedule for what's coming up on ABC in the next week.
As you might expect, the HBO GO app also only provides access to HBO content. There are a lot of good HBO series, though, like Entourage, Curb Your Enthusiasm, and Game of Thrones, and it is nice to be able to stream them to the iPad from virtually anywhere--even sharing a 3G connection using my iPhone 4 as a Wi-Fi hotspot.
Netflix gives me access to a wide variety of TV shows, but it tends to be more of an archive of older seasons, and shows that are no longer on the air. For example, on Netflix I can watch all 249 episodes of The Andy Griffith Show, and the complete Star Trek, Star Trek: The Next Generation, Star Trek: Voyager, and Star Trek: Enterprise series.
On my iPhone, I also have access to CBS shows through the TV.com app, and to a variety of shows through the Uverse app compliments of my AT&T Uverse subscription. Unfortunately, TV.com doesn't have an iPad app, and the Uverse iPad app doesn't stream content--citing legal issues.
Another option for TV viewing is Hulu Plus. The app is free, but you have to pay for the Hulu Plus service, which I don't use, so I don't have the app.
The Netflix and HBO GO apps pull double-duty for both TV and movies, and the iPad Videos app offers another option for viewing movies bought or rented from iTunes.
Netflix is an established force for DVD and streaming movie content, so I probably don't need to go into much detail about what it has to offer. The HBO app provides access to a diverse selection of movies currently available from HBO spanning old and new movies from a variety of genres.
I am not a huge fan of the Videos app only because I think it should be merged with the iPod app as a consolidated media center. I don't want to go to iTunes, buy content, and then have to figure out which app to go to in order to use it. The iPod is outdated--both the device and the app. Apple should scrap it and make an iMedia app or something that rolls it all together.
I will say that I prefer to watch movies or TV shows using headphones. I don't mind listening to music over the iPad 2 speakers, but it is much easier to hear dialogue and follow the plot when you have headphones to filter out the noise around you and let you focus on what you're watching.
All in all, media and entertainment is definitely a strong suit for the iPad. There is no shortage of options, and frankly most of them are things I can easily do--or even prefer to do--using the iPad, but would never really think of using my notebook for (like reading a Kindle book).
Just as with the music apps, most of the other apps mentioned for TV and movies are able to stream content to a larger TV using AirPlay. When iOS 5 comes and the iPad 2 gets AirPlay Mirroring, the app itself won't matter and I will be able to put any iPad content on my TV--making the iPad a one-stop-shopping home entertainment device.