The best and most efficient software ever made is ZennoPoster, but:
Minuses:
1. You need to learn how to make bots (not so difficult, but you need 1 month of training to get experience).
2. You need to find niche platforms (blogs, web 2.0 etc) and create customs bots for each which is fast when you have experience, but still takes ome time.
Pluses:
1. You can get 90% success rates on anything you automate.
2. You can automate everything, especially platforms which Xrumer or GSA does not suport.
3. Basicly - sky's the limit
Example:
I used Xrumer to make profiles on Vbulletin forums. I took this ones which Xrumer couldn't reach. I've spent 1 week on making very pecise custom bot for it, including all possible fields, checkboxes and captchas that can show up (or not). And I've made a very precise text captcha reader and implemented mysql database with my own answers (in UTF-8). Effect ?
90 % success rates on making profiles, where Xrumer had 0%. Even chinesse or arabic text captchas were filled with no problems, but I've made text captcha database by myself (manually) using translators.