I am a home user who drinks mainly espressos, and make cappuccinos for my wife. Between us probably 4-5 shots a day. Have been crazy busy last few years with work/kids, so just using pre-ground reasonable quality coffee, including Illy, some supermarket espresso-grind stuff, and stuff from local roaster/grinder shop. Have a decent basic espresso machine (Gaggia Coffee Deluxe) which by all accounts should do the job, but was tending to get weak shots which ran through too quickly and a fairly thin crema. Had an unsuccessful purchase of a cheap DeLonghi burr grinder about 10 years ago, which was messy and difficult to use, and broke down quickly.
So did some research on taking the plunge and buying a new grinder. Was initially planning to spend in the £100 ($150) price area, but was disappointed to discover from reviews that most machines in this price bracket fail to grind fine enough consistently enough for good espresso. Ended up getting the Rocky from Coffeeitalia.co.uk for £215. Couriered from near Milan to Edinburgh arriving 5 days after order. Despite being extremely well double-boxed with lots of polystyrene chips, it had obviously taken a knock in transit and the grind button had popped out of the housing, and had become disconnected from a clip-in cable behind the switch, so machine not working. Excellent customer service from Coffeeitalia - online chat thing at 10pm when I went on their site, she said send an email, Matteo rang me 2 days later, talked me through taking the bottom off the machine to discover disconnected wire, problem solved.
The hopper on top of the machine turns en bloc to adjust in about 50 steps. I have mine set on about step 8 or 9 depending on the beans, for a good espresso shot in about the recommended amount of time. I am very impressed with the portafilter holder. My Gaggia portafilter sits nicely on there by itself and I find it very easy just to chuck a standard ~7g scoop of beans in the top and grind straight into the portafilter. It seems to me that for anyone who is not regularly serving up espresso-based coffees to large groups of people, the Rocky Doserless is ideal and very easy to use. No significant spillage so far, and easy not to waste beans. The doser option looks clunky and sounds a lot messier so I would avoid it unless you have a very good reason.
I considered spending an extra £140/$200 to get a Mazzer Mini. I think the Mini looks more the real deal, and I think if you were a true Coffee Geek (which I am not yet, aged 38, maybe give me a few years), you might apparently find more consistency in the size of the granules (i.e. all granules the same size, rather than a slightly broader spread of sizes). I'm confident I would not be able to tell the difference. I'm glad I bought the Rocky - I think the doserless option with portafilter probably works better for me than a Mazzer Mini would.
Also the Rocky is apparently better for cafetiere/French Press, set on about setting 40 - Mazzer Mini apparently struggles to get coarse enough grind.
Aesthetics - the Rocky looks solid and gives the impression it will last. It looks good, but not drop-dead beautiful.
Overall, so far I'm very happy with my purchase and have found it very easy to produce consistently pretty good coffee which is already a noticeable step above what I was drinking before.
Consider a Mazzer Mini if you are an expert barista who is obsessed with the perfect espresso, or if aesthetics is your thing, otherwise go the Rocky.