Changes to Plugin Configuration
You must now set your main Thingspeak API key via the plugin configuration menu. If you would like to enable Twitter integration, enter your Twitter ID here (you must also enable Twitter integration via the Thingspeak website, under Thingspeak Apps).
Changes to Device Configuration
Devices are now linked to existing Thingspeak channels by selecting the appropriate channel from the dropdown (eliminates the need to manage individual API keys for each channel, instead relying on the main user API key which is now entered into the plugin configuration settings)
Each device can now update on its own time setting (this was a feature request that took me entirely too long to implement).
Twitter integration will only work if you have configured Twitter via Thingspeak Apps (on the Thingspeak web site) and also in the plugin configuration.
New Tools to manage your Thingspeak Channels:
There are now several tools that you can use to manage your Thingspeak Channels, accessible from the plugin menu.
For example, when you select the Update Channel Info tool, a dialog will open which allows you to make changes to an existing channel.
The list of available channels will be pulled down from the Thingspeak server and once selected, the fields will be populated with existing information. Changes made to the information in these fields will be re-uploaded to Thingspeak when you click the Update button. The other tools available here should be pretty self-explanatory. Use these tools with caution as once the changes are committed, they are final!
Hopefully the new functionality is worth the price of admission. Please post any questions or bugs related to this update here.
ETA: The plugin documentation has been updated to reflect these changes.