I'm going to break this review down into the groups of people I'd highly recommend this to:
(1) If you just bought the 2017 Surface Pro, I would give this pen some heavy consideration before you buy the Surface Pen. I tested this pen with the Surface Pro I bought. For $30 less, this pen is so smooth, glides like butter across the screen. The Surface Pen has the "tilt" feature and double the levels of pressure, but honestly I think the tilt feature is just a novelty and you will not notice the difference in pressure levels. What you will notice, though, is that the Bamboo Ink pen is just a hair less laggy than the Surface Pen. The Surface Pen has come a long way in terms of reducing latency, but for $30 less, it's hard to argue against the Bamboo Ink except in two areas – first, the Bamboo Ink pen will not stick to the side of your Surface like the Surface Pen will. The Bamboo Ink pen also doesn't have an eraser at the tip (instead you'll have to press a button on the side to erase). If those are dealbreakers for you (understandable, especially the eraser part), go for the Surface Pen. But if saving a bit of cash while still having a phenomenal, smooth experience interests you, you honestly can't go wrong with Bamboo Ink.
(2) If you have a Surface Pro 4, Surface Book, or Surface 3 device, and you've lost your pen or want to upgrade your pen, this is the one for you. I tested this pen with a Surface Book. Again, this pen doesn't have an eraser at the end, nor can you stick it to the side of your device magnetically, but this is a solid pen here. This is a miles quicker than pen that you're probably used to, the one that's supposed to come with these devices. Lag is noticeably reduced. This is just a wonderful pen.
(3) Finally, if you have any other device that can take advantage of Wacom pens, you need to shoot for this one here. I tested the Bamboo Ink pen with a 2017 HP Spectre 13'' 4k and the 15'' variant, and wow! Seeing your own handwriting in 4k is already amazing, but on these devices, it's just like pen to paper. It's hard to put into words how great it was. Buttery smooth. Accurate. Beautiful. I'm definitely a fan of the Bamboo Ink with devices in this category. This is so much better than the included pen HP gives you, just fyi. More comfortable too.