I personally have used Garage Kept Motors (GKM) out of Grand Rapids, Michigan. The owners, Jeremy and AJ along with their staff are all true enthusiasts so they are passionate about what they do and in general all things automotive. They also are very honest and upfront so their reputation really helps them sell a lot of cars. So that said yes I recommend them if you live near them, or are looking to buy a car.
I found the experience I had letting someone else sell my car was very positive. There are some costs involved, but bear in mind generally these dealers get a higher price for the cars they sell over private sellers. Most dealers also offer financing so they can typically get a seller in the seat of car much easier then a private seller and using financing option to help a buyer bridge their budget.
The crew from GKM came and picked up the car from my house and trailered it to their showroom. There they detailed the car, took the photos and videos and promoted the car across multiple venues. That cost roughly $450 upfront, then I paid 15% commission on the sale. They handled getting the car shipped, transfer of title, talking to tire kickers, etc. Literally, the car left and I just waited for the check, no hassles! They did so well on the sale, that even after commission and cost, I made out the same, or even better then if I sold it myself.
I also recently bought through a dealer, Ross Customs out of Goodrich Michigan. Ross also was a big car enthusiast. He loves cars, has a restoration shop, was professional, yet personable and very upfront. Since I paid cash he worked me up a great deal as he owned the car and was not consigning it. So bear in mind some dealers may just buy your car upfront, understand it may be below market as they need to make a profit.
My advice in finding a dealer is check out the reviews online, then talk it over with the dealer about all costs, fees and the consignment rate. It varies from dealer to dealer so shop around. Also ask how they market their cars and where. Finally, do a gut check, after all your research and conversations, do you feel good about it? Does the dealer and have a passion for cars? These dealers are the kind of people that draw other enthusiasts as buyers and sellers. In the case of GKM they have repeat big dollar buyers and collectors who consign amazing cars. My experience is this is true of other passionate dealers who are equally successful.
Wayne Carini (Chasing Classic cars TV show, Hagerty columnist, etc.) runs F40 Motorsports.
On the show, you get the impression he does consignments and not just "buy your car and flip it".
Selling a car can be a hassle and the human interactions are not for everyone. So there is value in consigning depending on yourself.
If I lived near Wayne or had a really high-end car I might use him. I don't (lol). But I would be looking for a consignment dealer with a good history in the business. I wouldn't be consigning with someone responding to my online ad with "I can sell that car for you".
Couple of concerns about a consignment dealer;
1.Your title. I would advise keeping your title and car fully insured until they can present you with a cashiers check for your car. Have seen dealers close shop after they sold your car and walked off with your funds and never registered the car for the buyer. Dealers mismanaged their business and got behind on bills and took the money and run. They can declare bankruptcy at any time and you would not be aware they were in trouble.
2. Understand that you will never know what your car sold for. Dealers put incredible markups on these cars so they have plenty of wiggle room. They could sell it for more than you wanted, not tell you and add their 10% commission on top of that. If you just want a bottom line figure that might work out for you. This is done frequently at Boat/RV consignment dealers and same principles can be applied here.
I personally will only buy classics from pvt. parties due to bad experiences with consigners, BAT and Ebaymotors.
I'm happy to see in this thread that someone found a trusted consigner, but that's not my experience.
I agree with Jasonsrq that consigners frequently add incredible markups. I've seen cars listed for $83K sell for $58K. Perhaps they are fishing for the impulse buyer (who may have just finished a martini?).
I've seen them renege on deals and misrepresent vehicles. Some examples are a high end restoration shop presented me a 993TT as a <10k mile car. I asked about the car on Rennlist and a Rennlister told me how the car had been totaled, rebuilt on a salvage title and then retitled. I had a consigner renege on price, the car had drive train problems and then I read some press about the seller and ran from the deal. A seller on BAT presented a pristine 1K mileage 41 year old motorcycle. Once it was bid up someone commented that the exhaust was not OEM. I guess the seller didn't feel obligated to disclose. It worked for him since he got way over the Hagerty estimated concours price.
If you use a consigner I hope you get a trusted personal recommendation. I'd also do some background checking. I found a number of criminal cases on one consigners record including forgery of vehicle titles.