I am using them for the first time this August. I did search on here and ask around before booking with them. They are an authorized WDW vacation planning company based in NJ. They buy up blocks of rooms at low prices, so that is how they get those discounts. The tickets they offer are "convention tickets", which are totally legit, but not as flexible as a MYW ticket, so again, there is a savings there.
Once you book with them, they forward you the confirmation straight from Disney. You can then use that confirmation number to go on
MDE and view your reservations, link them to your dining, etc. The only thing I can't do so far is make a payment on Disney's website. I was able to book all my ADRs, and DME, and already got my luggage tags, etc.
So far it's been an easy experience!