We use Yealink phones in our office and recommend it quite often to our voiSip phone service customers.
They all have a nice, heavy, solid feel. Everything fits and feels tight.
The screens are easy to read with a simple layout.
The speakers in the handset and speakerphone are high quality and sound very nice.
The operation is responsive and works great with all the features of our IP PBX systems... music on hold, transfer, conference, voicemail, etc.
There are several similar models... here's what you need to know about each.
NOTE: If it has a "P" in the model name, like T22P vs T22, then it supports PoE (Power over Ethernet). Which can be handy in some environments.
The T18/T18P is the lowest price model, but has no LCD display, so it has limited potential.
The T20/T20P has a basic display, 2 line buttons, and works great as a single endpoint phone for business or residential use.
The T22/T22P is really the best choice for a standard extension phone though. It has a slightly larger screen than the T20, 3 line buttons, and 4 context sensitive soft buttons. The soft buttons are very handy when used with an IP PBX system. But probably not important in a stand-alone situation.
The T26/T26P is the same as the T22, but adds 10 programmable buttons/lights for speed dial or extension/line status. It also supports a "sidecar" expansion module if necessary. Great phone for a receptionist or someone who needs to monitor line status... or just needs a lot of speed dial buttons.
The T28/T28P is like the T26, but with a larger screen and 6 call status buttons/lights instead of 3.
The 32G and 38G models are like the T22 and T28 models, except they have really nice color screens and gigabit ethernet ports. These are great for high end offices, though the prices are surprisingly reasonable.
The EXP38 and EXP39 Expansion Modules add more status lamps and speed dial buttons. The 38 is the standard type with red/green lamps, and paper cards for extension names. The 39 is well worth the small price premium though, since it has LCD display of names... no more scratch outs. It has a handy page swap feature, so you can have 20 lamps/buttons for one page, and 20 on the swap page... 40 total on one module.
Hope that helps. Enjoy your phones, especially if using them with voiSip phone service.