After falling in love with Oli Larkin's freeware Autopan I purchased his Endless Series + Spacestation bundle and the latter is really worth the money on its own. No matter if you try to dramatize drumloops or give a fairy-like touch to vocals it's always convincing by panning the input between two locators within the stereofield which you can move around any way you want. You can tap a button and start the panning once in a while or toggle the tap-button to pan all the time, which confused me the first time as I didn't hear anything but besides that the gui is pretty self-explanatory and if I'd have read the friendly manual... well.
Besides Spacestation being a simulation of the Doppler Effect it is a highly configurable autopan-plugin as well as the doppler-effect can be turned off by turning the pitch slider to 0. While using the Doppler Effect there is a Warp-feature that lets you add varying dissonance to the source as it passes by, so with the optional reverb and delay units as well as a choice of curves for the signal path, for the duration & the direction, one-shot or loop mode you can mangle a signal and sit there for a long time forgetting you started just panning. Most parameters can be automated, the only thing I am missing here is the automation of the locators so this is why it doesn't get a 10 for its features.
I haven't digged too deep into all its possibilities so my judgement about its sound might be a bit vague but when you just use its panning functions w/o the Doppler the crispness of the attack of a chord e.g. gets lost and the overall impression is a bit muddy (the same source keeps its original sound and timbre in Autopan so I guess this is an aspect of the Spacestation I just didn't get).
Stability: while using it in Live 3.01 I never experienced any problems as long as I didn't try to drag'n'drop it from one track to another, this causes Live to freeze. It seems to freeze anyway in SoundForge 7 (according to Oli this could be a bug in SynthEdit), but it works like a charm in Tracktion.
Besides that, there is NO reason at all not to give the demo a try and to buy.