Some more for you:
Frame spikes galore. The drivers and/or tech isn't mature enough for 4K yet. It's a terrible option for it.
Thank you for the frametimes, but you are making it sound that the card cant even play games well. It was already mentioned by amd that this problem is beeing adressed.
At 1080p even if not perfect i never faced any problem with frame latency, of course that you can "feel" some spike here and there mas nothing that would hinder the gameplay since they were too far in between.
Crossfire and frame times improved alot now that the the card comunication is done trhu PCI-E, not perfect but yet but a great start since with improved alot the problems that 7970 and below faced when in crossfire mode.I still remeber the nightmares with the 4970, never done crossfire again until R9 series.
I am speaking of my personal experience, im not speaking from some frame latency graphs.
Maybe some people are more sensitive to this question than i am dunno.
Even with 20% less TDP you will run into heat\noise problems, in the summer you must choose one heat or noise unless you go WC. Just seach for 780ti sli temps and you will see plenty of statements, the same for 290x as well.