There are some new tools that are pretty amazing for CS5. First off, let's talk about the new perspective grids. Once you start playing around with this option it makes you think "This program has been around for over 23 years and they are just NOW coming out with this?" (Obviously, long time Adobe users remember the Vanishing point concept of Photoshop CS2 and its subsequent evolutions with After Effects. It's good to see some of these improvements populating to all the programs in the creative suite!) It is an awesome new tool to create perspective drawings easier than ever. With this feature whatever you insert into the grid will automatically match with the perspective plane. I found myself playing with this feature for hours.
CS5 brings a new Shape builder tool as well, which I also found to be very helpful. It takes some time to get used to as it differs from the older pathfinder panel. Basically this feature allows you to create and merge shapes while also being able to delete portions to create new shapes.
A new brush is finally added to the paintbrush options from CS4: the Bristle Brush. This allows further use of the paintbrush with the ability to customize. With this new brush you can change your tip shape, opacity etc. The results are very nice and very organic.
This new version also brings up some additional upgrades from CS4. Some are small and may even go unnoticed as of this review, but the multiple art board panels are something worth mentioning. This allows you to work on several panels at a time, up to 100 at a time! Which may be overkill, but I'm sure there is someone out there with that need. This also allows you to take graphics from one board to another quickly and with ease.