Intonation on a floating trem, definitely. I'm cr@p at intonation on anything, but on a those it's particularly nasty.
I know people hate changing the strings on floating trems, but I generally just change one string at a time until they're all done, so it's very easy to get it back in tune afterwards. I used to use an old cassette box to rest the bridge on and change them all in one hit, but that doesn't work on my Jem with it's recessed floating bridge, so one string at a time works best for me. :)