studioone107 wrotei checked over and over and cant find any new features in the artist 4 version.
Definitely worth it IMO, but YMMV...
With Artist v4, you are getting Impact XT and Sample One XT and the creative workflow that comes with those. Basically, that's $25 per plugin and great integration inside S1.
You also get the drum editor and pattern editor, which are pretty good, especially the pattern editor IMO. I also think you get the ARA2 integration, for when the next Melodyne comes out.
I don't know about track notes, but you might get those too.
There are also a bunch of other little refinements here and there.
So definitely worth $50 IMO, and you can get a discount at some online shops, around 10-15% off, so that makes it no-brainer territory if you think you might benefit from those new tools.
Cost less than £100 for me for pro. If it's not worth upgrading now it may well be next year, the chances of getting it cheaper are slim.
Even if it was just for support it would be worth it (£33 a year maybe).