The Quick navigation allows you move around channels quickly by arrow buttons or tapping on the left/right side of log views. Arrow buttons indicate events (highlight, new message coming or new PM coming) happened in the other channels. So you can recognize it easily while chatting in another channel.
LimeChat features such as iOS 4 multitasking support. Connections are kept in 10 minutes after going to background, Quick navigation, Arrow buttons indicate events (highlight, new message coming or new PM coming) happened in the other channels, Highlights messages and optionally vibrates for your specific words, Visual interface for user information (whois), Built-in browser for clickable URL links, Full support for landscape mode, Stay connected while iPhone is locked, Multiple servers and channels, Automatic Nickserv authentication support, Full support for many text encodings, SSL support, VoiceOver support, Easy-to-read log views, Keyword highlighting, Stability, etc..
LimeChat is compatible with iPhone, iPod touch, and iPad. It's requires iOS 3.0 or later. The price is $4.99 to buy.