Microsoft then screwed up their next natural keyboard called the Microsoft Natural Multimedia. It defaulted to using the specialized keyset MS had introduced (help, undo, redo, new, open, etc) rather than the standard function keys, which were on the same physical keys. Brilliant and forward thinking, right? Because soon everyone will be using those instead of the stodgy old F1-F12 keys. *bzzzt* Wrong! And of course, there was no way to change the default in software, so every time you turn it on or reset the computer, you had to remember to turn on your damned function keys. That keyboard sits on my audio workstation, because apparently I'm too cheap to replace an otherwise perfectly good keyboard that has just one irritating flaw.
I currently use the MS Natural 4000 model on my main workstation, and really love it. Hopefully they'll continue selling it for a long time to come. If not, I'll probably buy a dozen of them and hoard them for the rest of my life.
I also like and use the MS Natural 4000, but it has the same "F lock" behavior that you dislike about the MS Natural Multimedia. The F keys default to being Help, Undo, etc... and you have to press the F lock key for them to work as regular F keys. And apparently F lock always defaults to off and can't be changed through software (though apparently you can kludge something up with the Intellitype software that remaps MS's special keys back to F keys--but it doesn't work for programs that use the raw scancodes, e.g., games that use DirectInput).