It was excellent, but flawed. I was glad I saw it in a theatre, in IMAX.
It was one of a small class of excellent science fiction movies where the science is important to the story and mostly actual science.
It repeatedly pays tribute to 2001: A Space Odyssey, one of the few films in the same category. But in 2001 the first and last parts of the movie are about alien science so advanced that they are, for us, indistinguishable from magic. And for the last, so incomprehensible that you can't understand what's going on without buying the book.
The middle third of 2001 does not violate science, except when it does. The moonbus follows a very unlikely trajectory because that is easier to film. If such a craft existed, it would have been launched in a ballistic trajectory from launch to destination, with no effort to maintain constant altitude.
According to the book, it was a surface vehicle, with very limited ability to launch over obstacles. Also not easy to film.
Discovery had no radiators because the director thought the audience would mistake them for wings.
Doing good cinema and good science at the same time is hard. I count Contact in this select group, but still its wormhole opening technology was close to magic.
My biggest complaint about Interstellar is that at times it was hard to understand important words spoken.
There are some plot holes, but fewer than some people think. The ice that astronauts walk on on the second planet is probably unreasonably strong. Keeping the secret space program secret would be difficult if all the launches came from the base used for the final launch, but perhaps there were other, more remote launch sites.
Some have complained that if the Ranger spacecraft can reach orbit with a single reusable stage, why do they need a big two stage chemical rocket to get it into Earth orbit?
It seems that according to the film's site, the landers use both chemical and plasma rockets, and NASA has fusion reactors as a power source. If the reactor uses He-3, the limited supply would explain the two stage chemical rocket to reach Earth orbit.