I am sorry to hear about the difficulty porting your number from Vonage to Ting! We may be using HPC2 to replace the existing lines at dozens of locations. I suspect we will experience a few porting issues as well, but the savings will make the hassle worthwhile for us.
I have tested the various features of the HPC2 and written a full review describing my experience with purchase, setup, activation, and usage of the SHPC2.
In short, I believe the HPC2 will work well for us and have had only had two major surprises:
#1 - The device does not support Caller ID name, which was already discussed earlier in this thread. If you have a telephone handset that supports Caller ID, it will display the number but it will NOT display the name.
#2 - The HPC2 uses 3G data service to download firmware updates. The HPC2 is the only device activated in my account and my Ting.com dashboard shows that I have used 1 megabyte of data. I spoke with Ting today and they do not (yet) provide the option to disable data access on the SHPC2, so my account will be charged $3/mo for up to 100 megabytes of data. This is not a huge concern since the $3/mo will be shared by dozens of devices and my plan will likely include other data devices in the future. However, someone who is expecting to pay $9/mo ($6/mo device + $3/mo 100 minutes) may be disappointed when they are charged $12/mo ($6/mo device + $3/mo 100 minutes + $3/mo 100 megabytes). I am hoping Ting gives customers the option to disable data service for the HPC2 device.
I have also read that the HPC2 does not support fax machines, credit card terminals, or alarm systems. This does not affect us because we have moved to online faxing, online credit card processing, and cellular or IP-based alarm systems with the intention of moving away from "landline" phone service. This may be an issue for other people though? I suspect the devices may work at lower speeds (e.g.: faxing at 4800 baud, credit card processing at 4800 baud, etc). It would be nice to hear from someone who has tried to use these devices with the HPC2.