If you don't mind parting with cash, then I can recommend Serif Drawplus X4 (which is what I use), it's about £60 and has most of the functionality of Adobe Illustrator, is pretty stable and has a very easy learning curve. Another one to look at as well is Xara which Gamerprinter and some others use. If you have loads of objects using filter effects you are going to get a slowdown, whatever application you are using as the effects need to be redrawn everytime you make a change and the calculations your processor has to do can get phenomenal. You can (in Serif anyway) disable the effects to speed up rendertimes and enable them again when you want to see you image in all its glory.