I have read Segue's website, about their products. They seem to cover everything (1) functional testing based on UI automation, (2) load testing and (3) component testing for components that do not have a GUI. So, if I were to buy these tools, will there be situations where these tools are not sufficient and I will still have to write custom test drivers for automating such things? If yes, what are some of the examples of things that cannot be automated by Silk tools?
Also, I am interested to know what are the limitations of these tools before I buy it.
Everything including test automation tools have limitations.
Gael is correct with her answer - regardless of tool - identify your requirements for an automation tool - work with the vendors to do proof of concepts on your own applications - choose the tool that works for your company and applications.