Normally when doing macro shots like this, the depth of field is almost paper thin, meaning anything in front or behind this this zone will be out of focus. If you take multiple exposures at different planes, you can stack the images by only selecting the in-focus portions of each image and assemble them into a complete single image.
Very nicely done. What equipment please? I'm in the market for a set of rails and I haven't decided which to get yet.
USM IS you are right the manfrotto rails are not the best on the market I have a set and when I used them I found the only effective way was to have the locking screw turned so that there was always pressure on the main screw. It makes turning the screw (and thus moving the rail back and forth) slower and a little harder but it means that you get far less of the frame shake since you are not having to adjust the pressure screw.
If you want a set of better rails I would say get a set of the hongkong ebay rails (also sold by Adorama as Adorama focusing rails). The velbon focusing rails might also be another good option but I have not used them.
Also for the lighting in this shot how were your lights arranged? I'm not too sure that the dark upper section works well enough - it gets the impression that its blending into the background but not desirably.