PartyGaming, the internet gambling firm that's merging with rival bwin, has traded in line with expectations during the fourth quarter, with a stronger casino business offsetting weakness in poker and bingo.The company said trading since the end of September has been "solid" overall, thanks mainly to casino's double-digit growth in average daily gross revenue versus the third quarter.There was also growth at the poker business quarter on quarter, but the usual seasonal pickup has been "less pronounced" due to the euro's strength against the dollar. Both bingo and sports are down on Q3.But clean earnings before interest, tax, depreciation and amortisation (EBITDA) margins for 2010 remain in-line with previous guidance of 27-28%.And the company is excited about the possibility of online gaming being regulated in the US both at the Federal and State level. If it goes through, the group is "well advanced" in talks with licensed companies in the US that could create "substantial" value. "The proposed merger with bwin remains on-track to complete at the end of the first quarter and should place the combined group in a strong position to take advantage of the changing regulatory landscape in Europe given its leadership positions across all key product verticals," boss Jim Ryan said.