I slogged through about 4 episodes, and didn't "give up" per se, but also haven't gone out of my way to catch up thru On Demand. I guess that says something. Horse racing is a pretty arcane world most people are not familiar with. In the real world, horse racing tracks have been closing all over the country due to lack of interest by the public. So the series had made a mistake in concentrating on that world, and taking too long to introduce sub-plots that are more intriquing or suspenseful.
What's more interesting is the question: will this be the end of HBO's relationship with creator/producer David Milch? His last creation - John from Cincinatti was a mess of a series, and was very low rated.
Before that, Milch also created Deadwood for HBO - a great series and a critical favorite, but a bit of an acquired taste for most viewers. That was cancelled after 3 seasons (IIRC), reportedly because it was 'too expensive' to produce.