Hey Scrumptious...
I love Illustrator!!
• you can work in layers and then file>export into a .psd to add Photoshop stuff.
• Try and avoid doing drop shadows and stuff in Illustrator - do all that in P.shop.
• The 3D filter comes in useful sometimes...but then Object>Expand Appearance and put on layers to render in PS.
• You can also do stuff in PS then save as tif etc. and place in Illustrator.
• You can write text and then Type>Create outlines.
• You can also bring in photos and create vector graphics using the Trace tools etc.
• The pathfinder tools are great/useful - play around with some shapes and see what the tools can do.
• You can create vector stuff and then save for web, or PDF etc...and both PS and Illus work well with Indesign.
• You can create vector stuff and save as swf. for Flash etc.
• Then there's the pen tool - worth getting to grips with (similar to PS one).
I do some CS3 tutoring so if you need any help, just ask...hope this gives you a vague taste...I often work between the two apps for my work...they both have their merits and work well together. As Wiz says, learning anything takes time...and as YPiggy says, practice makes perfectish - there's a treasure trove of useful stuff in Illus.
Some sites that may be of usefulness:
http://livedocs.adobe.com/en_US/Illustrator/13.0/
http://www.blog.spoongraphics.co.uk/category/tutorials/
http://www.senecadesign.com/designgeek/illustrator.html
http://www.taterboy.com/blog/2008/06/10-adobe-illustrator-tips/
Keep chopping!
Mx