Sorry for reviving an old thread.. but I thought that I would just give my thoughts on the topic.
Around August last year, I found a really great deal on a Slimblade and I couldn't pass it up. Brand new up opened box for less than market price. I absolutely loved it.
Such a difference from my M570. Now I love the Logitech M570, but I found the Kensington such a pleasure to use. The scrolling feature is nothing but genius. Its so intuitive and became sort of muscle memory within seconds of initial use. So I highly recommend the Slimblade.
Now, here is a caveat for you. The Slimblade switches are incredibly flimsy and in less than a year, two weeks ago, the bottom left button just stopped working. Thankfully it is still under warranty, but I live in Dubai and such devices are hard to come by. The shop offered me a Kensington Orbit with scroll wheel as an exchange device. I told them no deal. I either get another Slimblade or my current one is repaired. If no Slimblade is available, I will accept an Expert or an Elecom Huge.. But nothing less.
This in no means suggests that the Slimblade is lesser. I did post a video of an Expert making a weird buzzing sound on its switches. Also there are reviews where others have been using their SBs for more than 3 years with no issues. Therefore I am inclined to suspect that I just got a faulty production piece.
If they do give me an Expert, it will give me a chance to find out which of the two I prefer.