Big booster IMO, if this continues there should be some of the highly established and popular gambling sites and businesses taking bitcoin as one of their currencies, suggesting and encouraging gamblers to learn and get BTC, So indirectly this should boost bitcoins in long-term.
Big booster, but not that big to be significant IMO. Some people gamble using BTC to evade gambling regulations and restrictions on their country/region. Also, others find it easy to cash out winnings using bitcoins rather than cashing out dollars as is because big withdrawals on cash were often questioned really hard due to fraud regulations and whatnot.