Not sure why the IP phones were necessarily better than an ATA. If you bought 4 IP phones for $99 each, it would mean ~ $400 for making your whole house with voip.
I bought and setup a discounted ATA and connected a 3-handset cordless DECT 6.0 phone all over the house. Total cost under $90 including the cost of the ATA. All this with voip.ms and vbuzzer. If I want more handsets, I could buy additional DECT 6.0 handsets and expand my phone system to up to 6-handsets. But that is overkill.
I am keeping my Bell landline because I realized that I needed the landline as a backup, and for home security systems e.g. ADT, which requires a reliable phone line i.e. landline. A cellular based security system is more expensive if available (so this was ruled out), and some security systems do not work well with voip phone lines as reported by many users.
I believe IP hardware phones like yours are great if one has the money. The above works well for me and so far, I'm pretty happy with my low-cost setup. I like yours as well, but its costlier.
Panasonic TH50PX60U / Denon AVR-990 / 8642HD PVR/ Panasonic DVD-S77 / Pioneer DV-563A / Playstation3 / Belkin PF60