I recently had to open a simple Illustrator file in Inkscape and it worked well enough. But yeah I wouldn’t be surprised if it choked on more complicated stuff. You can of course always ask your clients to save as SVG.
I found that SVGs between Illustrator and InkScape aren't fully compatible either. Sometimes objects wouldn't get filled in the same way. Most problems seemed to be on the Illustrator side, though, not InkScape. Or maybe the other guy didn't quite know what he was doing, but still that's a real problem, and he isn't dumb either.
I bet you'd get all sorts of minor glitches and artefacts with even more complicated vector imagery.
