Do take advantage of demo or evaluation copies of the software. You'll lose a lot less if you buy one license and decide the product doesn't meet your needs than if you buy fifteen. Don't be swayed by vendor hype. All automation vendors promise amazing results in virtually no time. The vendors must be referring to how long it takes to automate testing of applications with one form and five lines of code.
Real applications take real time to automate.
In Make sure that you communicate clearly with your management about the goals of automation. You want management to buy in to both the idea of automation and your specific objectives. If you ensure their support up front, you are likely to get the software and machine resources you need to use automation effectively. Over the last several years, it seems that few development organizations question the need for test automation. Management is more likely to question a given automation strategy than the need for test automation in general.