We chose to use Sauce Labs as our Selenium Grid in the cloud b/c we didn't want to support testing on Windows/IE in-house due to security concerns.

Thus choosing a service like Sauce Labs was the only solution we had to execute our Watir-WebDriver (Selenium) acceptance tests on IE and other browser/OS combos.

Pros: It took me a few hours to get setup and immediately start running tests. Our main test stack consists of: Cucumber/Watir-WebDriver (Selenium-WebDriver) and getting it up and running was not that hard. It was very fast to spin up a VM and run tests and view the screencasts and screenshots. Easier to use this as opposed to setting up an in-house Selenium Grid setup.

Cons: I didn't find ANY documentation on how to setup Watir-WebDriver on Sauce Labs, I had to figure it out via Googling. The Watir tests do run a tad bit slow on SL. The UI is a bit dated, tried out the new beta UI and it looks nicer but doesn't seem to be ready for production use, the screencast view in beta mode was way too big.

Overall I like it as it's easy to use and gets the job done. I have yet to setup w/Jenkins, that's the next stop.