First, the wizard is easy to use making the learning curve for simple ETL tasks nice
Second, since Informatica is mature there are a good variety of connectors available
Finally, we have driven some fairly complex ETL solutions using only Cloud
The wizard, although easy to grasp, is very buggy. Many, many times we've lost work because of a bad page refresh or we click a certain sequence of options the UI didn't like. Very Frustrating.
One can save jobs within an environment but you can't backup your jobs locally, for example download the XML to duplicate or copy jobs around. And the feature to migrate jobs from one environment to another is unreliable and, when successful, only copies portions of the config. Almost always easier to rebuild from scratch. This makes moving from DEV to TEST to PROD difficult and, more important, undermines the QA process.
User community is not as active as one would expect with such a large customer base.
No one I have had experience with uses IOD by itself but always has a team leveraging PowerCenter to do complex work.
Informatica was recently purchased by a private equity firm. The jury is still out as to what impact this will have although it usually does not bode well. If you want to use what everyone else is using, this is your product. If you're looking for a flexible ETL suite, continue your search.