Kahlers have issues mainly because they are the a misunderstood;)
they advertise them as a simple drop in on a strat, which they are. But they dont point out the optimal saddle height for the bridge... because believe it or not the bottom half of the height adjustment is not going to work to well. If you put one on a strat with very little neck angle you would probably assume you could set the saddles low since that adjustment is there. . . If you do you definately loose sustain and string may pop out the saddle as it doesnt give a nice amount of downward pressure.
Once you get the saddles at a nice height (about 10.30 on a clock) then your action would be very high on a strat. A neck shim is needed. Not a problem but something people miss because they think they have it adjusted well within its range.
I like kahlers when they are set up properly. I have a 7200 which is a USA factory made trem and i really like it. The guitar its on has plenty of sustain (how much do you need?) so even if the kahler is robbing some its not an issue. I like the softer feel as well - although it is leading to me bashing the trem arm into the body a bit too frequently :)
I have just ordered a 80's kahler flyer - which i believe is the model that had the most issues with sustain - we will see.
Not all floyds are created equal.. and strangely not all kahlers are either. This is their comparison chart
http://www.kahlerparts.com/Other_Pages/Compare.htm