Mallard is a derivative of another very popular Heartland brand, made exclusively for Camping World. CW decides what features and options to make available so they're slightly differentiated in the marketplace. Judging from posts here, I'd say that they sell a lot of Mallards and most are happy with their purchase.
Before you take delivery, do a thorough walk through where the CW employee shows you how everything operates and answers all your questions. They'll never have more time for you than before you sign the paperwork. You should ask them to show you the water heater bypass and antifreeze hose used for winterizing. Sometimes they're tucked away in places you might not expect.
If anything needs to be corrected, get it corrected before signing. Occasionally, there could be something where a part has to be ordered from Heartland. If so, make sure the commitment for that part is in writing so there's no confusion after the fact if there are personnel changes.
If you have questions after purchase, this is a good place to get answers. And we have a collection of owner-written user guides that you may find helpful. Here's a link.