It started with a good premise - the birth of the Cylons and the formation of true artificial intelligence. The pilot movie was excellent - it almost did too good of a job, it started with the shock of a terrorist attack and introduced an interesting set of characters through the impacts it had upon them.
It's real problem was where it went from there - the show veered away from what most viewers wanted to see. Pulling the Tauran Mafia, VR World and the STO to the front, pushing the development of the Cylons and humanity's dependence and misuse of them into the background, turned viewers away. Instead of the development of the Cylons we got a drama about religious fanaticism - this was often the weakest link of BSG and was not what people tuned in to see. Added to that, the plots often meandered very slowly. The times it hit on interesting ideas it wouldn't settle and examine them, just flit onto the next one. The other problem was its unending bleakness and almost universally unlikable characters, often making it a chore to watch.
Special mention has to go to the music - Bear Creary's compositions were excellent throughout, but while its melancholic tones fit the series well, it did contribute to the bleakness mentioned earlier.
A lot of the acting was good - this was easily some of the best stuff Eric Stoltz has ever done and good mentions have to go out to Paula Malcolmson and Easi Morales. Nice to see Teryl Rothery playing a mature role and very well it has to be said.
Polly Walker (Clarice) just had to play her usual conniving character, which she's great at but is hardly a stretch for her. While none of the acting was technically bad, the actors lumbered with Lacy Rand, William Adama and Sam Adama couldn't do enough with their poorly written characters to make them anything more than annoying.
Most viewers came in having watched BSG. From that point of view only the Cylons really mattered. We know all these societies are destroyed - Tauron, Gemenon, Caprica, etc - so interplanetary issues - civil wars, space mafia, VR worlds, etc are dwarfed by future events. The STO and their 'one god' beliefs are related naturally, but we already know they are 'right' from this universe's point of view and as they appear to operate with no conscience, they are one dimensional and act 100% evil - the lack of any grey area was a complete shame.
Towards the end of the season we could see the various threads weaving more closely together, giving some characters a hint of redemption, until we got a small but satisfying conclusion to the series. The epilogue showed the writer's intentions of where the characters were to go. Most felt right, although Clarice as a priest and Lacy as the Reverend Mother didn't really make that much sense.
People have discussed Caprica to death, particularly what it did wrong and why it lost its audience, but despite its shortcomings it was often intelligent, dramatic and while it didn't do thrilling as often as it should, when it did, it was great. More sorry to see it go than I would have expected but hopeful Blood and Chrome (if that name stays) will bring bigger, better BSG-related action.