I've been noodling around with a few vector based designs this weekend (makes a nice change from coding). When if comes to vector I've never ever got on with illustrator as it's alway seemed a million miles away from the the photoshop interface. A while ago I played with Freeverse's Lineform app about the time it first came out and found it to be incredibly easy to use.
To start with today I was using Vector Designer, which is another simple vector app which I had lying around as it had come as part of a software bundle. However I was finding it to be a touch limiting and when I was looking to align nodes in a path I couldn't find a way to do that. Hitting that block made me think of Lineform and so I instantly downloaded the demo to give it a spin.
Overall, Lineform has a lot finer grained controls for vector objects and I found it's also very intuitive - the gradient tools in particular are wonderful. It also follows mac interface conventions well which always makes one feel at home. Whilst I also like Inkscape (which is an open source vector application) I do find it's interface quite clunky in comparison. Additionally it only currently runs under x11 which makes it less that ideal on a mac. Whilst Inkscape is clearly extremely powerful in the right hands (definitely not mine!) there's a lot to be said for stripped down interfaces that help you get what you need to do done. It's in this department that Lineform excels. That being said Inkscape is well worth a look as an alternative - and it's free so you can't say fairer than that!
The one downside I found with Line form is that the control over type seems slightly limited in some specific areas (I particularly found there doesn't seem to be an interface which provides control over horizontal letter spacing). Despite this I would say it's a very compentent app for getting vector work done efficiently, especially considering how much it costs. The current price is a reasonable $79 and if like me the low value of the pound is biting hard then there's currently a $30 discount if you enter "lineform30" at the checkout.