When SGU was launched, fans of its predecessors, Stargate SG-1 and Stargate Atlantis expected more of the same. Namely, a team of intrepid heroes has exciting planet-of-the-week adventures while fending off evil and suspiciously human-like enemies, such as the Gouald or the Wraith, with FN P90s and lots of explosions. SGU broke the mold with its more serious look at space exploration. We could no longer magically understand aliens (what few there were). Technological societies were not present on every planet but instead were quite rare. To me, this made the encounters with the alien all the more exciting.
Robert Carlyle's Dr. Rush was no Dr. Carter, or even Dr. McKay. And Louis Ferreira's Colonel Young was no Jack O'neill or even John Shephard. The SG-1 protagonists were extremely likable and heroic, and while McKay and Shephard had some issues with other people and authority, respectively, they were still likable and heroic. Variations on a theme. The SGU protagonists are more like real people. Deeply flawed people. Rush is selfish, cunning, abrasive, brilliant but not impossibly so, and at times just fundamentally unlikable. Colonel Young is insubordinate, moody, often unprofessional, but military through and through. Both characters are far more interesting than their predecessors. The other cast members are good but these two and their diametrically opposed world views really steal the show.
Unfortunately, too many fans of SG1 and SGA hated they didn't get another carbon copy spinoff and campaigned so much against SGU that creators tried to appease them bringing back fan favorite Rodney McKay, but such efforts were ultimately too late to prevent series cancellation.
Personally I like all the Stargate series, but this one is by far my favorite. SG1 and SGA are fun, but ultimately meaningless, asking few serious questions about morality or the nature of our existence. These are topics explored in abundance in SGU. Indeed, the (unfulfilled) mission of the Ancient ship Destiny was to answer such questions. Meanwhile, each episode delivers various challenges to the crew's survival, ranging from seemingly mundane problems like lack of water, to microsocietal problems in the Rush/Young camps, to exotic and exciting problems like being hunted by aliens and Berserker drones.
The way the series ended left it possible this show could be picked up again. The actors are about a decade older, but logically the characters could have aged as well after the events in the Season 2 cliffhanger. It's my hope somebody will give SGU a proper run or at least conclusion.
This series is a little slow to build up, certainly compared to its predecessors where galactic-wide war breaks out more or less in the first episodes, but give it a chance and you won't regret it. Just don't go in with the expectation SGU is like SG1/SGA, or you will be disappointed.