I have had my KX3 for about 2 months and love it. Having NR, variable filtering, CW decode for the fast ones only scratches the surface of pluses over my 817. With that being said the KX3 sets on the desk, back porch or other protected area (don't have money to replace it). My 817 sits in a go bag for field use since it does appear to be sealed against the elements better if it does get a little dusty or starts to rain. So my opinion is both have their place and neither is going anywhere.http://gemsproducts.com/covers.html
The KX3 is a much better performing radio and the FT-817 is more rugged and cheaper to replace. I do not use 2m or 70cm very often so that is not a consideration for me.
might be of interest to you.