Watchable because it's fast-paced, and full of intrigue and double-dealings. The actors are young, good-looking and earnest as they try to breathe life into some hammy dialogue. But they grow into their characters as the series progresses. Episode 4 and 6 are especially absorbing, when the storylines and conflicts all gel.
As for scientific plausibility, that goes out of the airlock long before they hit the big red FTL button, but who cares when it moves so fast?
There's some corny humour and overworked stereotypes (e.g. geeky genius that talks to plants). And the pseudo-military trappings are straight out of BSG.
All in all, solid entertainment with no pretensions.