In Korea, Free-iSMS is popular. This software's cheap price(through group purchase:about $4~5) and good compatiblity with Korean SMS system are attractive. But clumsy scrolling is stuffy.
Thread SMS is similar with iSMS : chat-style SMS client. If you interested in this app, you can have test version here.
Basically new-message popup is supported.
(Buy when you use SlideUnlock together, lockscreen doesn't block popup. It's slightly inconvenience. -_-;)
When it first starts, some sessions arranged by contacts list are appear. If one session tap, messages in the session are appear. Yellow star mark means unread message. Through chat-style view and comments, conversation was convenient than original messaging client. Kinetic scrolling effect responded very smoothly and shrewdly.
And.. smiley list was cute. :-)
In Professional ver., some function was added. Check here.
Anyway, ThreadSMS 1.96 Lite version(not Professional ver.) is slitely uncomfortable for use. So I think it can't replace original message client. If it compatible with Korean SMS-system well and some bug fix, it'll much popular for Korean user.(It means some serious problems exist on lite version and hard to use in Korea.)
Korean SMS-system is ridiculous than other country's. Up to 90bytes process SMS, over 90bytes process MMS(Multimedia Message Service.). Over 90bytes message was received and try to read it, ThreadSMS Lite exits abnormally. And then, when I tried to delete session(includes MMS) on app, all messages was deleted but session title was existed.(-_-;) Furthermore, after abnormal exit... I couldn't delete MMS on original message client. An error message was appeared. Only reboot and not to run ThreadSMS can solve this problem.
Plus. when I tapped vacant area on session-select page, last session was seleted. And tapped again, the session's messages was appeared.
I think app's function is great and scrolling was wonderful. If it fixes these problems, I want to use this with main message client. And if it support Korean language, I'll be very happy.
p.s. "Loaded SMS count" bug exist. When I set over 400, app was exit abnormally.