First off, I would rarely award a full five stars as I like to save them, but I can see why a number of others have chosen to award five stars to Centrale Bellagio. It is not a full amenities place. If you full nine, like a work-out room, fancy room service, bathrobes, a view of the water, etc you should look to spend (a lot more) elsewhere (like the Hotel Belvedere). Centrale is a gem, almost more like a Bed and Breakfast than a hotel. An excellent choice we were very, very happy to have made.
It starts with the friendly, attentive father and sons who run the hotel. From the delicious coffee (esp. cappuccino) they make to order at the morning breakfast to answering any travel question you might have, they genuinely seem to enjoy interacting with and helping guests.
Rooms are cozy, airy and bright enough (face it you will be out during the day!). Comfortable bed, nice shower and bath products, smallish but adequate closet to hang clothes. Incredibly quiet, esp. given its location in the heart of Bellagio. We stayed end of August beginning of September, and while there were a number of other guests, the hotel still felt intimate. Near a produce store and small market as well, a bonus for my vegetarian wife. Computer for Internet access was handy, with former guests contributing to a "travel library" in case you might still need a few tips. Breakfast is serviceable but pleasant, with yogurt, cereal, some crossiants (occasionally a bit overcooked sorry), fruit, some meats (I did not try), the aforesaid excellent coffee, and if you're lucky, some special "cake" involving pine nuts, dried fruit, and walnuts -- sort of like a moist banana bread (but no bananas). We actually took a couple extra pieces with us for a nice snack during our hikes in the mountains above Menaggio. A welcome treat!
The hotel connected us with a driver service for E120 return to Milan, which, given our morning flight, I HIGHLY recommend (lets you stay another night in town and avoid the ferry, train, bus negotiation).
All in all a strong recommendation and worth your consideration and patronage.