Hi
I'd recommend a Panasonic KX-TGP600 usually supplied with the handset type TPA60, especially for anyone who likes to tinker as you can get at loads of settings.
The handset is a step up from the usual consumer plastic affairs you tend to get now and has a nice premium feel. Very easy to keep clean as there is no printing on top of the phone (the buttons are clear and printed on the reverse) so no fear of wiping off the lettering or trying to clean around rubber buttons, plus backlights really nicely as well. Screen is bright and clear and it has an LED indicator that flashes to get your attention (message left or missed call).
Panasonic keep the software up to date and it has been 100% reliable with Sipgate. Works really well if you have multiple numbers as easy to pick "a line" to call out on.
Our copper telephone line has gone now as on FTTP, so it is our landline now. No one has noticed any difference calling us on it, and message waiting indicators work with Sipgate.
In terms of hardware, as is the trend these days, VoIP phones use a design/chipset from the same few companies, the Panasonic is using a VoIP chipset from DSP, and in this model they use DSPs top of the line
chipset DVF9919 .
Regards
Phil