Canadian visa agencies like canadianvisaexpert - are the legit or should I fill out the visa forms myself?

From some googling (and memory from when I applied for a Canadian WHP visa), they're real, but they have a LOT of complaints. Scambook's page on them:

Information about Canadian Visa Expert was first submitted to Scambook on Dec 09, 2012. Since then the page has accumulated 157 consumer complaints. On average users reported $1647.53 of damages. Scambook's investigation team reached out to this company a total of 2 times, Scambook Investigators last contacted them on Feb 05, 2013

They also receive a B- on the BBB, having had a few complaints registered there, with at least one resulting in a full refund.

Read into that what you will.

To be honest, I did the process myself. The first time I did it I made a mistake, left out something blindingly obvious, and they just sent it back immediately - not rejected, just with a note to add the extra item. So it doesn't mean you can't apply again - I certainly did.

I don’t know how you got to canadianvisaexpert but have a look on this from C.I.C http://www.cic.gc.ca/english/department/media/notices/notice-fraud.asp

What you need to know:

You do not need to hire an immigration representative to apply for a visa or for Canadian citizenship. Immigration representatives do not have special connections with Canadian government officials and cannot guarantee you a visa. Only authorized officers at Canadian embassies, high commissions and consulates can decide whether or not to issue a visa. Don’t be tempted into using false documents as this will result in the refusal of your application. Beware of internet scams and false websites. The official website of Citizenship and Immigration Canada (CIC) is www.cic.gc.ca. You will find free application forms and guides for any type of visa on CIC’s website. Processing fees are the same at all Canadian visa offices around the world. Fees in local currency are based on official exchange rates and correspond with the amount in Canadian dollars. Canadian visa offices will never ask you to deposit money into an individual’s personal bank accounts or to transfer money through a specific private money transfer company. If you have questions, contact CIC or the visa office responsible for your area.

To read more, including information on who can legally represent you if you choose to hire an immigration representative, check out CIC’s web pages on Immigration Representatives.

if it is so important for you, use a lawyer. They must be committed to you as a client. Much more than an agency

look what they say here

http://www.cic.gc.ca/english/information/representative/rep-who.asp

Paid representatives

Only some people can charge a fee or receive any other type of payment to represent or advise you on a Canadian immigration or citizenship proceeding or application. These are:

lawyers and paralegals who are members in good standing of a Canadian provincial or territorial law society,
notaries who are members in good standing of the Chamber des notaries du Québec and
citizenship or immigration consultants who are members in good standing of the Immigration Consultants of Canada Regulatory Council.

These people are called “authorized” representatives.

CIC will not deal with representatives who charge for their services and are not members of one of the above groups. Other people who offer paid immigration or citizenship advice

Anyone who gives you paid advice before you apply or start a proceeding must be authorized. Unauthorized people must either become authorized or refer you to someone who is.

If you pay a representative, they must be authorized if they:

act on your behalf during an immigration or citizenship proceeding by speaking for you,
help you choose the best immigration stream or
fill out any forms.