second look surgery?

My wife (61) was diagnosed with ovarian cancer (stage IV) in January, and had debulking surgery shortly afterwards.  Her CA125 dropped from about 185 to high 30s.  She began chemotherapy three weeks later, but had a severe anaphylactic reaction to the taxol.  She was switched to a combination of Gemzar and carboplatin that apparently worked.  She tolerated the regimen well.  She had the last of six cycles about a month ago, and her CA125 steadily dropped to 17.  Recent chest x-ray and CT scan showed no new or recurrent tumors.  We understand, however, that some tumors may not be detected through imaging.  My question is "Where do we go from here?"  What are the risks and benefits of second look surgery, continued chemotherapy, and "watchful waiting?"  She's come a long way, and we don't want to jeopardize the considerable gains that she's made.