I haven't been able to use their free service since the day where the transaction fee increase a lot.
Someone is probably abusing their free service by using a bot, since their captcha challenge is so easy.
Well, there are other free tx accelerator I used but I am not sure if it really works or not.
I hope you are not referring to transaction rebroadcasting services masquerading as transactions accelerators. They are so many of them. The only working free transaction accelerator that I know at the moment is probably ViaBTC.