The best thing about guest line is that there are no additional charges for adding new features to the system after you have subscribed it.
Also they offer good customer service by providing solutions very fast if required. We had one issue where we were not able to get our hotel reservation confirmation through email but later found out its because of some problem in their server which was resolved quickly and within few days I got my emails sent from them again. If anyone wants complete control over all your hospitality related needs then this would be great option as many other companies charge extra fees especially when compared to others like HotelsCombined who provide free services at once place unlike anyothers!