I agree with the above.
It's not something that is necessary needed, unless you have a complex case... However, if you are using a good lawyer, or even consultant, it can be beneficial - for lots of people.
I used one and I'm happy I did. There were several errors I made - granted they were minor... However, overall I'm glad I choose to use one.
If you can afford it and have any concerns, it won't hurt to go with one. However, at the same time, if it's going to cost you too much money and you don't think you need one, you really don't need to go with them. Just make sure you check your application a few times (against the instructions and docs check list) to make sure you haven't made any errors - especially serious ones!
These forums are pretty good - people will help you where they can. Also, the search function is great - this forum has years worth of information just waiting to be read!
Good luck.