After five years (purchased in July 2006) of nearly daily use and no maintenance other than cleaning, I am happy with my grinder.
Positive Product Points
The Rancillio Rocky is a beast of a machine; dense is perhaps the most descriptive term. The guts are mechanically robust with a powerful motor and a good set of bearings. The burr is well balanced and built to last. Relatively easy to clean if you have a source of high pressure air or CO2 and a small stiff brush. Maintains a setting without wandering and returns to give a repeat performance every time.
Negative Product Points
There is some plastic that will tend to crack and craze over time, but if you don't over-tighten the screws it should last a long time. Beans can get caught in the screw holes in the hopper baffle, but I found that I could put some foam earplugs in the holes and prevent the problem. The earplugs will last a couple of years. Because of the way the ground coffee is delivered to the portafilter by a set of rotating scrapers in an annular slot around the base of the burr, there will be a certain amount of coffee that collects in the grinder after each use. I found that I could force most of it out by making a piston/plunger out of two layers of corrugated cardboard cut to just fit inside the hopper and attached to a wine cork with a single drywall screw. I put as much coffee as I need (preweighed) into the hopper, set the grind, grind it until everything is done making noise, then run the plunger to blow out the residual ground coffee through the exit spout. It doesn't get it all, but it is good enough.
The little rubber feet are inadequate to keep this chunk of iron and copper (and stainless) from scratching a susceptible countertop. I had to put a piece of foam drawer liner (cut to shape) under the base to provide protection.
See below for comments on grind size. I think this is a design defect but you can work around it if you are careful.
My grinder came set up with a minimum grind size that was way too large for espresso. At the finest setting I literally could not tamp 14g of the resulting coffee hard enough to yield 20g of espresso in 25 sec of brewing time. So I had to remove the screw from the underside of the hopper (the one that acts as a stop to keep you from running the burr down to zero clearance). This allowed me to set it down about 4 more clicks (of which I use 3) where it grinds a nice espresso. My impression is that the factory should shim one side of the burr or the other so that zero is really zero (or within one click of zero) before they ship the grinders. So I went through a long time blaming the problem on other things before I finally figured out that it could not be anything else. I now have a grinder that works, but I also run the risk that somebody who doesn't know what "STOP HERE" means (on a little piece of strategically placed tape) will run the burrs into each other.
Cleaning is OK, but made somewhat difficult by the weight of the unit and the fact that the center of gravity is very low - so it is hard to turn upside down and shake/bang/brush out the residual ground coffee. On the other hand it only needs cleaning about once a month to keep from building up a cake of powdered coffee in the mechanism.
For espresso, you will by necessity be down near zero (-4 to +4); for drip I use 20g of beans ground at a setting of 20, and for French press I run at 40+.