In my experience irises quickly demand attention for use in a mixed border. I had two plants in a small bed dedicated to daylilies backed up by crocosmia and a handful of annuals scattered throughout the bed. For three years with all plants being young it came to be it seemed a perfect bed with just enough contrast but that fourth spring following I had to remove one iris and split the other. I tend to grow my irises in areas dedicated to only irises now. I can always go back to the old look with smaller starts and transplant them when the time comes. Maybe next year!
I also agree the iris foliage still has nice garden appeal throughout the season with very little maintenance required.