Most of you have already given good reasons why consultants should not be chosen, I'll add real example-
My friend had applied via consultancy, they told him that he just needs 7 in all IELTS and then they will go for PNPs- his score got to be 380~ and even after inquiring number of times they kept telling him to wait as score were coming down and PNP were going to open etc.
When he got to know i am trying and received ITA, he called me up, then he realized that they kept him waiting on this for 8-10 months- instead he could have given IELTS and gotten better score!
Talking about lack of time, well if one really wants to they can take time over weekend to research and gather info, there are so many helpful people here on this forum who provide advise as well. (Did the same myself)
Having urgency- this is genuine reason for going to consultants, but unfortunately most of them (at least in Pune) are money minded, and want to do least of work (self- experience: went to 3-4 of them but all had same process: they will take money,yes, but it was upto us to collect everything properly and they will just file the documents on the portal).
If you feel the agency is genuine in helping you and not taking your money, please take their help and also recommend the name here as others will also require the same.