I bought this head unit a couple of years ago and I only have good things to say about it. For a start, the head unit looks great, has an elegant, curvy form, and it has a detachable faceplate - which is a big plus for any head unit to prevent theft. Also, the sound quality is brilliant, and without going into a load of technical detail, it is certainly powerful enough. It is unlikely that your speakers will be able to cope with high volumes unless you have replaced your car speakers. It also has a fader for altering the front and rear sound balance, and other settings for boosting bass etc.
The head unit is very easy to program although it will require reading the instruction manual the first time. You can save up to 6 am and fm channels, which is plenty by anyone's standards. One criticism I would make is that the buttons are quite small and it takes some getting used to being able to do anything other than basic tasks whilst driving, and they also have different functions depending on whether you are in USB/aux or radio mode - so, again, it takes practice but once you get to grips with what everything does it's not much of a problem.
The main reason I bought this head unit is because I can hook up my ipod and control it from the head unit itself. If you'd rather flick through your ipod manually, you can do that too - and the best part is you'll never run out of battery because it charges the ipod while it's connected. I hardly ever charge my ipod because I have it hooked up in my car so much that its always got full battery! The head unit will display what song is playing, and you can change this to display artist, album or even the current song number in relation to the playlist size (14/82, for instance). One thing you probably won't be able to do with this head unit (unless you have a small iTunes library), is navigate your whole music collection. This is done easily if you set it to iPod control, but to try and navigate 100s, or possibly 1000s of artists/albums/songs is pretty time consuming when using the rotary joystick. It can take a lot of scrolling to find an artist/song in the middle of the alphabet...
It is also worth noting that this head unit doesn't require any extra hardware to connect your iPod - it works by plugging it into the USB using your standard iPod USB cable. This is a massive benefit when you consider that the extra bit of kit necessary for other head units (even Pioneer ones) costs around £50.
For people who are buying their first head unit, you must remember that you will need the head unit interface AND the vehicle interface in order to hook it up to your particular car model. If you want to use the steering controls, you'll need another piece of kit specific to your car, and you will need a head unit fitting, again, specific to your car model, however head units themselves are a standard size unless otherwise stated, so don't worry about whether the fitting will fit your specific head unit.
Like all other Pioneer units this has a superior quality and reliability that you dont tend to get with the budget units. For the price the unit is great value for money. If your looking for a stereo which you can hook up an mp3 player, or an ipod, but want one with a bit more to it, then this is the unit for you. Very easy to use, looks fantastic, and will not let you down. Again, like other Pioneer models, the tuning of the radio stations can be slightly annoying and hard to grasp initially but once you have overcome that small obstacle, you will not be disapointed. The sound quality is as expected from a Pioneer, giving the standard speakers a bit more...oomph to them, without distorting or sounding like they will blow. Overall a very good stereo, slightly more expensive than other with the same features, but i guess you get what you pay for!