Bought this for my Planet X road bike, and have clocked up 1200 miles (according to the computer) since I got it this year so I now feel well qualified to comment on this.
First, Cateye products are generally superb. This is no exception.
The people looking at this will fall into two camps- those who are after a replacement computer and those thinking- do I really need this? As to the second camp, the answer is a definitive yes. This is not a gimmick - if you intend to get semi serious about getting fit and enjoying your bike, you need to know how far you are going, the time taken and your average speed. In other words you need a cycle computer.
Now for both camps- this is a superb cycle computer and in fact is so popular it has become very common but for good reason. It is rock solid, and extremely accurate.
There are three parts to the computer. The first is a little magnet which attaches to the spokes of the wheel by means of a small hand turned screw. It fits both standard and flat spokes (I have it currently on my Fulcrum Racing 3 wheels).
You then have a sensor which is approximately 2 inches by 2 inches in size. This fits to the REAR of your fork. It has a rubber side which you place against your fork at the same height as the magnet on the spokes, so that when the wheel goes around the magnet passes by the sensor and records a revolution in the wheel.The sensor is affixed by means of some cable ties. If there is a fault, it is that you only get two cable ties (?- they cost nothing!). Luckily if you need more, you can get them from Amazon (you need 2.5mm width by 200mm long standard cable ties).
Next is the computer bit. This has a bracket which on a road bike would normally be affixed to the stem, although it turns 90 degrees so it can be fixed to the handle bar where necessary or on a bike without a long stem.
The computer clicks into the bracket and that is it- it is up and running. You will need to input your wheel size (chart in instructions) if you do not have a standard road bike wheel.
The computer has no buttons on the front and works by depressing the entire computer to switch between modes.
It shows various combinations of trip, speed, total mileage, top speed on last trip and time since set off and current time. It will also show average speed, and usefully at all times has a little arrow pointing up or down indicating whether you are travelling faster or slower than your average- gives you a kick up the backside if you are taking it too easy!
When you stop, i.e. at traffic lights, the time of that current trip stops.
So unless you want candence ( speed pedals are turning) this basically has everything you need in a reliable and highly rated package. A few people I know have one of these and no one has a bad word to say about them so you cannot go wrong.