I won't waste too much virtual ink on this review because it's very likely you won't be able to get your hands on this device.  But in the event you ever come across someone selling an Axiotron Studio Pen, my advice is simple: buy it! 

Axiotron was the company that first brought the Modbook to market in 2007. Modbooks are Apple MacBooks modified with Wacom touch screens. They're wonderful devices but very expensive.

Axiotron closed up shop shortly after the release of Apple's iPad. One of its founders Andreas Haas revived the concept and now markets the devices as Modbook, Inc. Unfortunately, the new Modbooks use a very basic tablet pc stylus I reviewed here.

The original Axiotron Studio Pen was much closer to the high end pens Wacom produces for its Cintiqs.

Plain Jane wrapping is nothing to write home about, but I include it here to show the model number of the pen I am writing about. Hopefully it will aid in your future online treasure hunts.

The Studio Pen is signficantly longer (6.2 inches) than other tablet pc pens. The Modbook Pro Digitizer Pen is 5.6 inches, the Motion Computing pen is 5.8 inches and the capped Wacom Bamboo Sylus Feel is 5.95 inches.

The Studio Pen is also flared, so it's approximately .10 inch wider than all the other pens I've tested at its thickest point. It has a dual button rocker with a large, comfortable rubber grip that's at least .25 inch longer than the grip on the Motion Computing pen.  And last but not least, the Studio Pen features nice big eraser tip.

The Axiotron Studio Pen (center) is the largest tablet pc stylus I've tested. Its replacement, the white Modbook tablet pc pen is extremely generic and too light and small for my tastes. The closest pen still in production is the Motion Computing stylus (second from bottom), but its grip and single button are much smaller. The Wacom Bamboo Stylus Feel Carbon is pictured at the top and the standard Surface Pro pen is at the bottom.

I found this pen used, so I'm not sure if the nib assortment was standard, but my pen came with a large array of hard, soft and flex nibs and even a replacement button and grip.

The Studio Pen package I bought used included a large assortment of replacment nibs, two extraction rings, a replacement button and a replacement grip. 

The pen is slightly lighter than the Wacom Feel, but its heft feels almost perfect to me. 

I can't find a reason to complain about the Axiotron. I'm just happy that I get to use it on the Surface Pro and my other Windows 8 tablets. Let's hope Wacom or Modbook see fit to offer something similar in the near future.

UPDATE: Reader Pat pointed out in the comments section below that the Axiotron is slightly less accurate than the Wacom Bamboo Stylus. I hadn't noticed this to be the case until I ran a side-by-side test. The slight offset of the cursor to the nib isn't terribly distracting and I quickly forgot about it as I began to draw. The only time where the accuracy becomes an issue is in targeting very fine points in the UI. As I mentioned in my response below, hitting the ultra-narrow scroll bars in Manga Studio is difficult with any pen, but nearly impossible with Axiotron.

Buttons on pens don't do anything for me. In fact, I think they're often a nuisance as I frequently find myself clicking them accidentally with my thick knuckles.

However, many of you swear by your pen buttons and I've been hunting high and low for a readily available Surface Pro pen replacement that will accommodate your needs. I've tested five pen replacements to date and none have more than one button. And the three higher end pens don't even have eraser tips either. 

Thanks to a tip from reader Steven Weitz, I finally wrapped my fingers around the replacement stylus you've been clamoring for, although you'll have to pay a relatively steep premium for the privilege.

That pen is the Modbook Pro Digitizer Pen, which retails for $70 from the Modbook Store. The plastic pen is virtually identical to two other pens I've reviewed previously: the Wacom Penabled Tablet PC Eraser Pen and the Samsung Electronics Slate PC Digitizer Pen, both of which cost about 50% less than the Modbook pen.

Modbook doesn't offer any precise specifications, but the pen is 5.5 inches long from eraser to nib and is very light, weighing about half an ounce, just like the Wacom and Samsung stylii. I can only assume that Wacom produces all three pens as the nibs are interchangeable as well.

Modbook clearly charges a hefty premium for its boutique product, but they at least offer a generous selection of nibs: five felt, four pencil and three stroke tips. The stroke tip is grey with a small spring.   According to Wacom, these nibs are supposed to provide a more "brush-like" feel.

Packs of five nibs cost $5-$10 from Wacom, so the additional nibs are definitely welcomed.

Performance is very consistent across all the tablet pc pens I've tested. Some users have reported that one pen is more precise than another, but I haven't found that to be the case in my testing. With calibration, every stylus displays the same accuracy.  

I personally prefer heavier, slightly thicker pens that are closer to real world instruments. However, any of the replacements I've identified will offer a more satisfying experience than the standard Surface Pro pen.

I appreciate that the Modbook Pen's button is angled high enough from the pen's barrel to avoid most accidental presses. And assigning button actions is a simple matter of finding the Pen Tablet Properties in Control Panel.

I'm told that there are other two-button options out there, but I think most of them are for older devices and not easily obtainable. So if you absolutely need that second button, the Modbook Pro Digitizer Pen is the way to go.

Each Modbook Pro Digitizer Pen also includes a pack of pen tips, containing the following:

5 × Felt tip (Black) 
3 × Pencil tip (White, factory installed) 
3 × Studio tip (Grey, spring-powered) 
1 × Pen tip removal tool

Except for its dual button, the Modbook Pro Digitizer Pen is almost identical to the much lower priced Samsung (above) and Wacom pens (below).