Funny - when someone says "trust me" - it usually means the exact opposite. Case in point here.
What mgmt actually said is that they are investing in growing their consulting business - which helps them push more high margin product. Consulting carries lower margin, so the increase in the lower margin business could have a slight negative impact on gross margin - based on mix. But as it is incremental revenue, it means an increase in gross profits, operating margin, and EPS.
In terms of operating margin, the company expects low 30's for Op margin in the 1H'14, and high 30's in the 2H'14 - which is in line-to-above FFIV'S historical operating margins.