I have a serger and it is the least used of any of my machines. I rarely use it in quilting , and then it is only because I happen to have it handy.. not that it is really needed. There is nothing in the quilting world that I am aware of that you can not do with a regular machine, that would require a serger. It would be the last thing on my list of additions to my quilting gear.
I'm a tools kinda gal ... so if it me I would spent the money on tools that would be more use to you on an everyday basis.