Adobe released the Alpha of Apollo a few weeks ago and there have been many reactions to the product and Flex in general since. Additionally, Adobe updated Flex.org to make it easier to get started with Flex.
Flex.org was updated this week to provide easier access to people seeking to learn about Flex. They created pages targeted to developers from different backend languages including Java, .NET, PHP, Ruby and ColdFusion. Additionally they have integrated FlexSearch.org
The developers of Buzzword have written about choosing Flex to create a new web-based word processor. They cite the need for a WYSIWYG application as the primary reason they have not done something similar to Google Docs. They're looking forward to Apollo to offer a hybrid online/offline version of their application.
Alexander Snaps has written about some concerns he has over backwards compatibility as well as single-vendor lock-in. The comments on his post offer a comparison of how Java and Flash have both done a good job at backwards compatibility, while both have had occasional problems. Flash is generally limited to a single installed runtime while with Java you can run multiple versions concurrently, should a compatibility issue arise.
Lastly, Scott Barnes, a Microsoft Developer Evangelist for RIAs, points out some resources for .NET developers looking at integrating with Flex.