Re: It was a success in that all guests came.
It's OK but it's a little odd. It makes it sound as if the only successful thing about it was that everyone turned up. The suggestion is that the rest of "it" was not a success.
Was your party a success?
Well, it was a success in that all the guests turned up. But there was a fight, a window got broken, I found my girlfriend snogging another guy in the bathroom and someone spilt blue curaçao on the white carpet.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.