Apple had a pretty good quarter in the April-June period. It pulled in $37.4 billion in revenue, with a quarterly net profit of $7.7 billion, a healthy increase over $35.3 billion in revenue and a net profit of $6.9 billion in the year-earlier quarter.But there's one thing that could keep CEO Tim Cook, new CFO Luca Maestri and the rest of the Apple crew from high-fiving: limp iPad sales.