Or is it a question of finding ways to make it scale and not a question of "if"?
1-. Keep on asking for feedback for your product and adjust it 100% to what your first users want
2-. Go for the wow factor. Make their product amazing (think about an iphone design)
3-. Make sure these early adopters use your product everyday (or as many times per week as they can). This will make them talk about your product with others.
- give discounts to the early adopters and to the new users when an early adopter refer to someone the product
All the best!