Highly Enjoyable . . . with the right attitude
First things first. If you watch this series, be prepared for extreme amounts of silliness and over the top reactions. This series practically goes for broke when it attempts comedy. Also, be prepared for the human sidekick (I know, we all hate the human sidekicks to mechas.) While Shute can get rather whiny at times, he does actually contribute to the team in his own way so he's better than the type of character who's just there to put a human into the main cast.
All this said, when it attempts some semi serious story arcs, it quite surprisingly manages to make them pretty enjoyable.
Plot: A kid called Shute gets caught up in an adventure when he witnesses an attempted invasion by an extradimensional force of robots known as the Dark Axis. Shute is rescued by a robot warrior (called a Gundam) and both find that they get along and that they compliment each others personalities. Shute is swept up along with Captain in a grand adventure to defend his world along with Captain (the Gundam who saved him). Along the way they meet Gundam's from other dimensions that have been invaded by the Dark Axis. These include a Knight themed Gundam named Zero from a Western Medievel themed land called Lacroa. Also joining them is a Samurai named Bakunetsumaru from a Japan-esque land called Ark.
They form a team called the Gundam Force and together they fight the Dark Axis.
This series is often looked down upon for being a primarily comedic take on a franchise that is usually much more serious.
Personally, I find myself enjoying it for the fact that it doesn't take itself too seriously all the time. Its comedy can be legitimately funny and part of the fun/charm comes from watching these characters interact with each other (even the first season main villains are far more funny than they are threatening).
The show goes in story arc mode, with one story arc taking place over several episodes. On the whole, the story arcs for the first season are adequate and even enjoyable. But everything takes a spin for the dramatic in the second season as the Gundam Force takes the fight directly to the Dark Axis. They don't abandon comedy, it's just that it gives more time for the story.
And personally, I think that the show does pretty good for itself, especially for some of the final story arcs and the eventual defeat of the Dark Axis.