At this point, is StubHub the only way to get tickets to Brooklyn Nets games?
Yes and no. The Nets have fast become one of the hottest commodities in the league, as everyone wants to get in on the first season. For some, getting in means getting into the building; for others, it means getting a slice of the economic pie. As a result, most of the high-profile games are already "sold out," and brokers (those that buy and resell the tickets) have put them up at a marked-up price on the secondary ticket market.
So if you're looking for the best matchups, to see the Knicks, Heat, Lakers, etc., you're out of luck going through the Nets. At this time, some lower-profile games still have face-value tickets available, though.