Take a look at their jobs page.
1. If they are hiring, that’s a good sign of growth.
2. If they are hiring engineers, that means that they are investing in building a better product
3. If they are hiring more sales people than engineers, they may be using sales to cover for a weak product.
(This is a general rule of thumb, not the only thing to look at.)
Example: We’ve started using Central Desktop. Current openings: 2 sales/marketing, 1 support, 3 engineers. Good ratio.