Forget about e-mail invitation - Only the public link works
The user interface is not of immediate understanding, but after spending many hours on it, I managed to use it and I've appreciated it. I chose this service because it said it allowed the sending of an automatic personal e-mail to the contacts on my list, but it never worked. The assistance replies once every 24 hours Monday-thru-Friday and was not able to solve the problem (given the little time to assist...). You can still use this service publishing a link where your survey is, but forget about tracking individual responses. I tried several other services advertising my desired feature of sending (and tracking) the survey by e-mail, but the only one which really worked was the famous "surveymonkey.com", but for the same period of the present service "kwiksurveys.com" it costs 2 times more, but, based on my experience, It'd really recommend it ("surveymonkey.com") if you want to keep track of "who has responded what" (and forget about all the others, not to waste time and energy for nothing).