I was happy so far with all features that were integrated into IPB by default but now I noticed I really miss one feature which is called: pin first post in topic so when you switch pages it would always display that first post.

Why is it important?

If we talk about meets or we have some kind of group buy, all important stuff would be lost or users wouldn't open first page after a while. So to stay always on top SMF has pin first post which on every pages comes always first.

I think that would be also very useful to other members as well.

Your control panel > Forums > Board Preferences > Topic Display Mode

Standard: Posts are shown one after the other.
Linear +: The first post is always shown at the top of the page, with other posts shown one after the other.
Outline: All posts in a topic are shown in tree display, with one thread at a time shown.

see also
Chaning viewing mode for subforum only

I know that but in SMF you can select only one topic which will have pinned first post on all pages in topic.

Shame that IPB doesn't have that option.