We've had a SWCG for about 18 months now and all I can say is that I'll never have a pool without one again. In spite of the good advice posted here to test the water frequently, I've gotten lazy lately and have been testing once every 7-10 days and the water stays...perfect. Yesterday's test results (my first full test in nearly a month) showed:

FC 5.5
CC 0
TC 5.5
pH 7.8
Alk 120
Cal 200
CYA 60
Temp 85

In the last 2-3 weeks I've added 16oz. of muriatic acid and done nothing else.
While I'm not recomending anyone get so lazy about testing their water, I couldn't been happier with the nearly no maintenance of the pool. The SWCG does it's thing and I can be pretty certain that if I'm gone for a week at a time, when I get home the pool will be nearly...perfect. Given my experience, for me it's a no-brainer. SWCG everytime.