we had a bid from one. They did beautiful work! I did feel limited a bit by their materials. I could only get the cabinet color I wanted in the super expensive custom line. And the bid was exactly double the other 3 bids we received. Pretty or not, we couldn't see how they were twice as good as everyone else.

I do like getting some of my own stuff; tile for example, so we went with someone who would let us pick and choose some things for ourselves.

There is no question the work would have been perfect and the designer could have handled some things I have to handle, but the value wasn't there for us.

We interviewed one (several times) when we did a large addition and major renovation. They provided some lovely ideas (the one we interviewed is high end.) We had someone else do our plans and put those out to bid, and it turned out that the design/build firm doesn't bid on anyone else's plans. So we went with another builder. We wanted to be able to compare quotes, and couldn't do that with the design/build firm.

I would never want to be limited by their "design center" showroom. But for non-picky folks, it would probably be just fine.

...is it worth it for the convenience of having someone coordinate and handle the whole project for you? Although we DIY the majority of projects around the house, cabinets and counters were something we felt best left to 'the experts'. We didn't want to risk making any costly mistakes on our own.

...are you limited in materials selections? I don't know how unique this is, but we were told we would not be allowed to visit the stone yard and pick our slabs (among the granite 'swatches' available to us). The owner told us if we insisted on viewing and selecting the slabs (who wouldn't?!), he would have to "put a KD" on our project. Really strange, and in hindsight, this should have been a red flag to us. While they had an array of drawer hardware and appliances displayed, we weren't required to purchase through the shop.

Just from the few replies you've received, it's clear every firm operates a little differently. Ask lots of questions and take notes. Above all, be sure to get references, and don't think a firm's competent based only on Houzz awards and 5-star online ratings. Good luck!