The Rich Text Editor fails to trigger the keyboard on my iPad, whilst Tony confirms a similar problem using the iPod Touch 4 (presumably iOS 4.1).
It's possible to enter text via the HTML tab but this is a painstaking task if you actually want multiple paragraphs, lists or styles of any kind. Also, as a web designer I'm familiar with HTML but I imagine most people are not.
The difference between the two tabs (Rich Text and HTML) appears to be that the RTE runs in an iFrame whilst the HTML tab runs as an inline Textarea.
I don't see why it's necessary to run the RTE in an iFrame.
Lithium is the only forum type I'm having difficulty posting on with my iPad (iOS 3.2.2).