I've had one for two months and have mixed feelings.
I've never been able to manage the accuracy required to sharpen anything freehand so I needed an aid to help me out. The Sharpmaker is really good at assisting with maintaining the two knife angles. It does take a little attention to make sure that you hold a blade vertical through the entire stroke, but it takes a lot less that holding a blade elevated off a flat stone. In that respect this product works really well.
However, it turns out I have a house full of neglected knives, scissors, etc. Not only are they not sharp, many are actually damaged with nicks out of the blade edge. In order to sharpen these edges, you need to remove quite a bit of material. The medium stones supplied with the Sharpmaker are fine for touching up a mildly dull blade, but they just aren't up to the task of removing lots of material, at least not quickly.
Further, it seems that most of the edges I have to sharpen aren't anywhere near preset angles that the Sharpmaker is designed to sharpen. I have some knives at just over 40 degrees. I have some kitchen knives that are chisel ground to around 12 degrees on one side (a little steeper than the 15-degree angle that the 30-degree edge is designed for). Of my 5 pairs of scissors (different brands), none of them is angle to match the 12.5 degree slot in the base of the shapener. For scissors, it isn't too hard to hold the cutting face flat to a stone since most are pretty broad. But for knives, if they don't match the 30 or 40 degree angles, you have two choices if you don't want to revert to free hand sharpening.
1) For edges that are a tiny bit steeper than 30 or 40 degrees
a) put a micro-bevel primary edge on them.
b) if you want to retain a nice chisel ground edge, the microbevel is not an option and you'll have to reprofile the blade by removing a lot of material at the blades edge.
2) For edges with an angle just over 30 degrees:
a) put a 40 degree microbevel on the edge
b) reprofile the blade by removing a lot of material at the shoulder of the edge.
3) For edges that are just over 40 degrees your only option is to reprofile the blade removing a lot of material at the shoulder of the edge.
Of course, reverting to free hand is always an option, but that sort of negates the system that this product offers.
If you do decide you want to reprofile or remove a lot of material to eliminate nicks, you are not going to be able to do it easily with the medium stones. I've tried, it's a time consuming affair. I have ordered a set of
these to hopefully address this problem. I hear that they make re-profiling blades much easier.
I know this review sounded fairly negative. But it's not a bad product. It just works well only if you have edges that are already in good condition and are at the right angles. If your edges are, then you're golden. Use this sharpener regularly to keep them in good condition. If you have edges that aren't, then you are almost necessarily looking at spending another $45-50 on
Diamond SharpMaker Stones or using a different product to do the rough reprofiling required to get an edge to exactly 30 or 40 degrees.
Update (2009-Jan-23):
I've received the Diamond SharpMaker Stones and used them for a little while. These really help a lot to remove material when steepening an angle or removing chips in the edge. Unless you have edges at the right angle and in good condition, I think you really need to pick up the diamond stones along with the Sharpmaker to have a versatile enough system.