I had used the included Intuos4/5 Grip Pen for sometime, and out of all the Grip Pens I have used, I loved my Intuos3 Grip Pen the best (closest pen equivalent right now is the Wacom Cintiq 13HD Pro Pen, which at the moment is not for sale as a standalone accessory.)
I recently purchased the Intuos4/5 Classic Pen for my Intuos4 XL.
First thing to note here is the pen is made in Japan, compared to the standard Intuos4/5 Grip Pen which is made in China. Another thing to note is the tip is slightly firmer compare to the grip pen (2nd gen sensor), which in turn provide a better minimum pressure range. But the firmness is nowhere near as firm as the Intuos3 sensor based pens.
The weight and feel is extremely similar as my Intuos3 Classic pens, and even the pen stand is identical. A note here, the pen will fit into the included stand, but due to the skinny girth of the pen, or wobbles slightly.
I really like the feel And the light weight of the pen. Though I wish the side switches are detachable or the pen comes in a switch-less version as the ergonomics would be even better (I never use those side switches anyways)
The pen works right out of the box. Once the pen gets in proximity with the compatible tablets or interactive displays, the driver will automatically register the pen's tool ID into your computer, and the preferences of that particular accessory will be saved.
Overall, a great buy. I use the Classic Pen as my main pen now due to the slightly better low pressure sensitivity as I rely on this a lot to produce pen line art.