I am currently using this model at my work. It has all you need out of an office phone and works perfectly well.
The dial keys are large and soft, so mistyping numbers is a thing of the past.
Sound quality is good, especially from the conventional speaker. The loudspeaker sound quality can be slightly tinny, but voice still comes across clearly when using that function.
The volume can be adjusted up or down at any point during a call and the phone remembers different settings for loudspeaker and handset volumes.
Last but not least on this section, it's worth noting that the phone is made of a very sturdy plastic that can withstand being slammed angrily into the receiver after being kept on hold for 20 minutes!
The best feature on this phone, which makes it stand out from the competition, is that you have a set of 15 buttons along the right-hand side which are not only programmable speed dials, but there is also an LED by each which indicates whether a person is on the phone (constant light) or being called (flashing light). This is particularly useful as it gives an indication of colleagues' presence in their office and whether they're engaged or able to talk.
The phone also comes with the range of features which you would expect at this price range: mute, last numbers dialled, redial etc. On top of these, it offers IP computer connectivity although, being an end-user, I can't say how easy that is to install and maintain.