My workplace finally got around to upgrading to CS5 (we're not an exceptionally high budget operation I can tell ya that) and my absolute #1 favorite most-used new feature as of CS5 is the variable width stroke.

Here's an explanation video from the Adobe website:
http://tv.adobe.com/watch/learn-illustrator-cs5/using-variablewidth-strokes/

In a nutshell for you who haven't clicked through, this feature gives you a separate set of handles that you can place along the length of your stroke to change its thickness at different points. For example, if you'd like your path to start very narrow, but bulge in the middle and then taper back to a point, you would start with a stroke with a very narrow width, then place a control point in the middle that's very wide. You also have control over either side of the stroke so if for whatever reason you only want to make one side of the outline thicker (this is especially useful for very sharp curves with very thick outlines) you can do that without changing your original path. This feature, in my workflow, has replaced all but special border and paintbrush brushes, and is miles beyond the current-from-last-I-checked Inkscape workflow of creating a shape to place along a path.

Of any improvements and features I could request for Inkscape, this is absolutely the number one. As clunky and unintuitive as the interface continues to prove itself, the quality of work this single feature could allow would still vastly narrow the gap between Inkscape and professional grade software.

Upcoming new feature for the next major release (0.49): Powerstroke

(Hint: basic variable stroke width (via LPE) already doable (though more cumbersome) in current stable versions (hint: use pen / pencil with a 'Shape', based on 'Pattern along Path' LPE) - see also this (old) video, and which path effects to use for that example in Inkscape 0.47 and later stable versions).

Ah that's fantastic! Looking at the release notes, it seems that lots of issues I've complained about for a long time are being addressed (despite certain users insisting they were fine).

I am aware of the Shape along Path feature but even before working heavily with Illustrator I thought it was cumbersome and clumsy. My only feature in PowerStroke that seems to be missing is the ability to independently control either side of the path. This ability in Ai has saved me loads of time. Any plans for that?

Luftmensch wrote:Here's an explanation video from the Adobe website:
http://tv.adobe.com/watch/learn-illustrator-cs5/using-variablewidth-strokes/

I actually described the mechanics of what you see in that video in 2008 - viewtopic.php?f=5&t=620&p=3192#p3192

Not that I'm suggesting that Adobe stole my idea--I'm sure hundreds of vector artists envisioned the same concept. But still, I'm awesome