If you want to know about the reputation or get reviews for any cosplay shop or commissioner, there is a Reviews subforum further down in the forum list. Check it out. It's very well organized.
That said, if you really cannot sew a stitch for whatever reason and don't want to take the chance at having to do ANY "tweaks" or "fixes" if your commission doesn't turn out right, don't use a large company. Many of them are overseas and while they will tell you anything you want to hear, they don't actually have a person dedicated to perfectly customizing your costume. They have a shop full of people working off more simplified patterns to mass-produce as much as they can before making any customized options. If you want the most control over your commission, you're better off negotiating with and hiring a commissioner who is in the same country of origin as yourself (for ease of shipping and customs/tax rates, as well as legal matters should a problem arise). Make that, a skilled private commissioner who will take all of your design sketches and ideas, all of your special tweaks, every last tiny detail you want included, and agree with you 100% on exactly what they're going to make and how they're going to make it even before you say "yes." They can discuss methods with you, they can discuss materials, and come to agreements or compromises if what you want isn't physically possible or may be expensive. They will also be up-front about costs and be willing to REPAIR OR REPLACE your costume if it doesn't turn out exactly like you want.
Do your research. There are a LOT of people offering commissions, some more skilled than others. Talk to them, send them emails, find out where they stand on custom designs and whether they know what they're talking about when they open their mouths. Be confident that your commissioner is going to actually produce the costume you're asking for and not something you're going to have to get fixed or altered by someone else for an additional cost. Every shop (and commissioner) will tell you they can do anything you ask for; you want to feel confident that they really mean it, that they know their stuff and are being honest with you instead of just attempting to get your money.
And that's why we have the Commissioner Reviews forum. Scroll down and check it out. You'll probably find reviews for not only the companies but also the independent commissioners, and lots of stories from people who might have had trouble with their commissions. You want to find someone who is agreeable and easy when it comes to fixing problems as much as you want someone who doesn't cause problems in the first place. Any commissioner who blames you for bad instructions or wrong measurements or doesn't stay in touch to help you if you really don't understand sewing and are not sure how to take measurements is probably not the kind you want to go with.
Founder and President, Madison Area Costuming Society, a chapter of the International Costumer's Guild
Strange Land Costuming - www.strangelandcostumes.com