I've ordered from them and have had good eperiences. They seem to have a pretty good selection and they are good about getting back to you if there is some kind of a problem with your order. I ordered some Black Friday sale stuff, and of course there were backorders with sales going on, but they let me know when to expect everything. It has now shipped out.
I ordered one item from them that did not match the picture, which was disappointing but fixable with an exacto knife. I emailed to let them know the picture was inaccurate and never got a direct response from them. I've noticed the picture has since been updated, though.
I still order from them, but not for anything where appearance is critical or where I have any concern whatsoever that I might need to interact with customer service (e.g. the size might be wrong and require an exchange). I suspect any issues *would* get fixed, but not as painlessly as at other stores.
But they're great if I am 100% confident about what I am ordering.
I've ordered from them several times and never had an issue. Well...except for the time my gallon of Rambo Wash exploded in the UPS truck or somewhere between them and me, but that wasn't Adams fault and they took care of dealing with UPS and shipping me a new one right away. Have to remember not to order such things in the cold time of the year...
I had a really crummy experience with them a few years ago and swore I'd never buy from them again. I've somehow gotten on their mailing list again and I have to admit I'm tempted to give them another try, since their prices are pretty reasonable. But I will only order if I'm sure I know what I'm getting and positive I won't need to return it. I don't think they keep much of anything in stock and it can be a hassle getting your money back on a return.
I always had great experiences with them. Prompt shipping and great communication. They are also incredibly supportive of the local horse community, including supplying all the stadium jumps for Maine's only USEA-rated horse trials! Really great people.