Sketchbook Pro is a fantastic program for artists and designers. It is uncluttered and designed entirely for a pen interface. If you don't have a tablet, you might find the interface a bit awkward.
If you do have a pen, you'll soon be wishing that every program was designed this way. The design lineage goes back to Alias, who created Sketchbook from the ground up to be an intuitive and extremely fast way for artists to communicate visually. Eschewing the cluttered interfaces of typical paint and photo programs, they focused on the bare bones of what the artist needs to put "ink" to "paper" and get the job done. To this end, those looking for full-featured painting programs might find Sketchbook lacking. The key word here, is "sketch".
Sketchbook Pro is fast. Pen responsiveness is top notch, giving you the most drawing bang for your buck. Without the enormous overhead of other digital graphics programs, Sketchbook Pro wrangles the most performance from even slightly older machines. You'll find that the software is easily able to keep pace with even your quickest or most subtle pen movements. Tool selection is equally easy, with "flickable" radial menus popping open instantly. While the austere interface can seem disappointing or shocking at first, it provides maximum ease of workflow, letting you make easy use of the entire page with less panning and zooming.
My problem with Sketchbook Pro extends to its Autodesk foster parent. Alias was swallowed up by Autodesk, and Sketchbook became somehting of a forgotten child. It received minimal attention with the Sketchbook Pro 2009 edition, which gave little extra to an already solid program. The Autodesk website, likewise, gives little indication that Autodesk even supports it, making it difficult for the new user to ge tinformation, check for updates, or engage in community forums with other Sketchbook users. This has improved, somewhat, over time. But, going to the Autodesk Technical Support page and looking at the list of products in the drop-down menu still finds Sketchbook Pro missing. This seemingly apparent lack of support isn't a deal breaker though, and there are Autodesk community forums with Sketchbook support, if you dig around. Autodesk does need to step up with their "old school" site design and make these changes more obvious.
For the price, nothing in the world beats Sketchbook Pro at what it does best: sketching and rapid drawing. With the 2010 version, some new tools add extra value, but perhaps not enough to make upgrading a necessity for longtime 2009 users. I use Sketchbook Pro 2009 to do rapid sketching and then port my roughs into Portalgraphics.net's "openCanvas" which I find to be a perfect companion. It supports all the same formats and has nearly as robust an interface, designs for pen use. It would seem that Autodesk took a page from Portalgraphics' openCanvas design, which has already supported canvas rotation for a long time.
Note: If you're looking for a good blend between rapid sketching and paint, with PSD support check both products, you may find both aren't necessary, with openCanvas being nearly as speedy and robust, and also offering a bevy of natural media pen and brush options, to boot.
I rate Sketchbook Pro at 4 Stars because it excels at everything it promises. The lacking 5th star is because Autodesk seems not to care very much. This program is clearly not their bread & butter, and as such, it seems to be constantly on the back burner, and receives minimal attention.
For the very small pricetag, you can't go wrong. Speed, ease of use and stability are the hallmarks of this program, and any artist with a tablet should have it in their arsenal. However, non-tablet artists are encouraged to stay away. The interface and design will, quite simply, make drawing even more cumbersome with a mouse, as it has no vector tools, and minimal "stamping" ability.