*The master output knob at the top of the GUI can't be modulated anymore.
*Limiter amount can't be modulated anymore.
*Modulating delay time with an LFO does not produce usable results.
In Reaper you can externally modulate and automate basically any parameter to your hearts desire - maybe not quite as easy and quick as via internal modulators but it just take a couple more seconds and works like a charm .
I have no idea what the OP (Simon?!) meant by 'useable' but I've been modulating the delay times with the built-in LFOs more often than not and they do the trick for me. YMMV.
Nuff for now.