I've added an option to enable this behaviour and as I looked at other IM clients available, I've made this feature enabled by default. It works on iPad and iPhone in the same way.

Moreover, I've decided to hide Send button displayed in the same line as text which user writes when this feature is enabled as return button is then renamed to @Send@. So there was no point to have 2 buttons doing the same thing on the screen. As a bonus, we got a little more space for text.

If this feature is disabled, then it is possible to use return key as in previous versions and there is no Send button on the keyboard (only @return@) and the old send button is displayed near text field (an arrow).

The feature will be part of the next snapshot build as soon as I will get crash reports for issues you reported and fix them.

Works great!