I drove out to Antelope Island and put in at the Marina about 7:00 that evening and I was the only one out on the lake. Note: driving out to the island on the causeway you smell a very bad odor of the shore line and decaying material, but as you get closer to the island the smell pretty much disappears.
The temp was about 94 degrees and the water was like a sheet of glass, I mean it was perfectly flat and not a single breeze could be found. The water as you know is many more times saltier than the ocean and it was kind of a brownish opaque color. (note I did not even attempt to roll because I did not know what the extreme saltiness would affect my eyes)
The draw back to this trip was the billons (maybe even trillions) of little brine flies that floated on the water especially by the shore. These tiny flies don't bite and they are not really attracted to humans, but the shear number of them can be troublesome. I was wearing shorts and a few would crawl on my legs while in the kayak (no sprayskirt) and this felt wierd but they didn't bite.
I paddled a couple of miles to the north and it was hot out there. I was going to paddle to Fremont Island and back but the heat and the glare from sun off of the water was relentless. So I cut the trip short. Be sure to carry a hat and water.
My kayak seemed to slice thru the salty water alright, but like I said the surface was almost mirror-like smooth. Some people have commented that kayaking in the Great Salt Lake creates some drag due to the salinity, but I did not notice any drag.
A side affect of kayaking in the Salt Lake is the next day I noticed a build up of salt crystals all over my kayak and paddles and a garden hose and sponge made quick work of this. (be sure to remove the salt crystals especially if you have a metallic rudder)
Overall a nice paddle, but be aware of the summer's sun and the brine flies. Also I bet paddling would be nicer if there was a slight breeeze which would help with the bugs.