I've used the Aastra 9112i (now discontinued), the Aastra 9480i and the Snom M9 DECT cordless.
By far, my favourite is the Aastra 9112i...it's carrier grade, solid as a rock and easy to use. The 9480i shares all the same attributes, but as a 4-line business phone, it's inherently more complicated a and cumbersome. It also doesn't require POE (AC adaptor instead), so I don't need to put costly injectors in my structured cabling system.
I will not be purchasing any more Snom phones...the recommended FW upgrade bricked my phone and it took tech support three days to send me an old FW file. Besides that, they are extremely light and don't have the sturdy feel that I like.
Im going to bench some Grandstream units next to see how they might fit in at the low end of the market. I'm also considering Cisco, but they usually require POE, so I might pass.