Illustrator is extremly helpful as you will find out. If you use photoshop then you will find it extremly useful there as well. Even more so than with MAX. I consider it the #1 proggy in the Illustrator-Photoshop-3D studio triad.
Anyway the main use of Illustrator is in texture creation. I create evrythng including banners, reg numbers, and other markings/details in illustrator, then copy-paste the work into the photoshop texture file. The advantage here is that if set up correctly then it will copy-paste at the right size into PS. First create a new document in Illustrator at 14.22 in x 14.22 in. This comforms exactly to a 1024x1024 px texture in photoshop. It wil then copy paste at the desired size.
I use illustrator to create cross-sections of hulls (save as Illustrator v3 *.ai, then import those into max, Import as seperate objects), works great!
Good luck and have fun Sandman. If you have any questions feel free to PM me or ask here.
Lord Schtupp