Looking for recommendations to use Rives Audio ...

I haven't them but have had numerous discussions with them about acoustical issues and have found them extremely knowlegdeable. Their website is quite good and their modeling tools are really to notch. I did the acoustics on my media room myself before hearing of Rives. I did months of research and talked to numerous acoustical engineers around the country. It was a very time consuming process. I did it because local av companies had no in house people and only offered the services of professional companies whose fees I thought were insulting. One of the top companies wanted several thousand dollars to evaluate my already constructed room and tell me what the cost of doing their treatment would be. Some of the material they were selling such as acoustical caulk at $50 plus per tube not including labor were items that could be obtained at home depot for $5 per tube ect. My understanding is that Rives sells advice and plans. If you don't want to spend a lot of time and gamble as I did I would strongly urge you to check out their prices. I was impressed with them.

I have not used them...yet; but just about all of my friends have had rooms designed by Rives or are talking to them right now about designing there room. I have seen blue prints and heard lots of great advice- when I am ready I know who I am going to call!

You could do it yourself...but then again my experience from 20 years in this business says that you'll not end up with as good of results that way! Letting an experienced professional with a track record do it for your is just about garanteed to give you much much better results!...every time! There's no replacement for experience...like in all things in life.
My dad always said, "when you need something done right, go to the professional!" My suggestion is the professional route.
I see easily 99+%(I'm very comfortable with that figure, trust me!) of the audio enthusiest out there ending up with not so good results, mainly because of lack of experience and knowledge! Should you find your self wanting to do it your self, and still wanting good, great, even world class sound quality be prepared to make it a very long time consuming endevor/hobby...otherwise, trade your money for time,dedication, and results!
Hope this helps

I'm in the midst of room construction via Rives. They know what they're doing and offer tailored advice. I doubt you would get similarly fastidious attention elsewhere.

"Was it worth the expense?"

You will have to evaluate your system and your future plans goals to know if the services are worth the expense as far as maximizing your system. E.g. if you've got a $1k pair of minimonitors (their basic analysis is like $800) and you're going to be moving anyhow or have a bad room I wouldn't do it. So "to try do it myself" isn't a bad idea depending on your system. It never hurts to educate yourself as much as possible and I think you can certainly get results on your own (through careful speaker/listener placement and liberal amounts of acoustic treatment). If you've got some big dollars in your rig then the services would most likely be worth it and the pros will probably do a better job. Especially when it comes to acoustic treamtent. Rules of thumb (foam at first reflection points) will get you some mileage but for serious acoustic treatment if the room isn't measured you'll probably be wasting money on things that aren't helping. Measuring rooms is important because its almost impossible to write an equation for every conceivable thing in your room (whether or not your walls have standard studs or box bracing, floor materials, windows, etc.)

Look at your system, your goals with it (are you going to upgrade speakers later), and how much money you plan to invest total.