You don't just want cash, you want cash & brains. You want smart people with knowledge of your market and the ability to help you succeed not just through money, but through advice, connections, etc.
To expand on this...an angel or series A round is not the end of your business, it's just the beginning. Cash can't tell you what to spend it on. You're going to need more people...possibly a CEO, probably a CFO within a year, a good accounting firm, sales people if you're in B2B, a PR firm, big customers willing to try your buggy beta software, etc. Knowing who to call on is part of what smart money can bring to the table. (You're on your own for legal...you can't share a lawyer with your money people, if you want to be able to trust things to shake out nicely. Like good fences make good neighbors, the same is true of good lawyers between money and businesses.)
