Inkscape is coming along nicely, but there are still a number of areas where it lacks in comparison to Illustrator. Depending on what you need to do with it, you may or may not encounter these areas.
Typographic controls - this is one area where you can really see a difference. You get the basic controls (size, leading) but you can’t control type width or tighten or loosen the kerning on a ‘global’ basis to your text block. In Illustrator, all these settings are controlled by parameters. The ability to have ‘paragraph’ text is also limited in Inkscape. You can choose to ‘flow into frame’ but then you lose the ability to adjust individual kern pairs. In addition. If you forget to link the text to the frame, you’ll lose the ability to change the text flow without re-linking to a frame. In Illustrator, you’d simply drag the text tool to set the text as ‘paragraph’ text as opposed to ‘artistic’ text and you can always drag and resize the paragraph boundaries to change the flow box.
Color spaces. Inkscape lacks CMYK so using it for pre-press is limited. A bigger problem (for what I do) is the inability to use spot colors. I wouldn’t even care if the spot colors are defined in the RGB color space, but when I’m doing logo design I want the ability to use specifically designated spot colors so that I can limit my usage to just those colors, as well as use tones of those colors. In the end, I’d be able to get plate separations where the colors properly separate to their respective plates. There’s no way currently in Inkscape to do this. All colors you add become independent RGB colors in the document, so you can’t easily change the definition of a spot color and have it updated in the entire document. In addition, you’d have to manually manage separations by working on different layers (not an exciting process.)
Unless I’m missing it, Inkscape also seems to lack the ability to define things with precise numeric control. For example, in Illustrator, if I want an offset path exactly 0.4 inches from my original path it is easy to do. In Inkscape, the offset is visual so you’d have to lay down a ruler or spacer object and ‘eyeball’ it. On the flip side, the ‘linked offset’ in Inkscape is an amazing tool in that you can have an offset path that recalculates when you adjust the original path. For “print people” they’d often just use strokes and wouldn’t appreciate this difference, but I am often doing stuff that will eventually end up being knife cut on a plotter and you need to have discrete paths for the knife to follow.
The floating panels in Inkscape bother me, but that may be more of a window manager thing in that they sometimes go to the back but then all reappear on top when I use one of them. In this respect, I wish other applications would think about the whole non-blocking UI of blender. I’d like the ability to have fixed panels as long as I had the ability to quickly ‘solo’ the main workspace (like Blender’s ctrl-up).
They finally added a ‘wireframe’ view in Inkscape in one of the recent releases (which I’m very thankful for) but there is (that I’m aware of) no quick toggle to turn it on and off. You have to go to the menu and select it each time. The ability to link that to a hotkey would be appreciated when attempting to line things up with stroke fills where you want to see the real path as well as the printed output. Illustrator has the view toggle on Ctrl-Y which allows a quick back and forth view option.
Overall, I like Inkscape and think it is coming along nicely - but there are a few things that leave me going back to Illustrator for my work. I’m sure there’s a few more things I forgot to mention, but these are the ones that I remember from some of the recent work I’ve done in it.
That said, I have Inkscape installed on my work machine (since my Illustrator license is my personal copy) and needed to do some Illustrations for a document I was putting together for work and was able to do everything I needed, so it definitely can be used for some tasks without problems. In addition, Inkscape runs infinitely better in Linux than Illustrator CS2 - so the choice may be made for you depending on your OS (Are you listening Adobe?).