hey there do it yourself,
You are definately not out of line to be upset. Undermount sinks are designed to be flush or within 1/16 of an inch shy of the inside of the sink bowls. Definately under no circumstance should the countertop overhang the sink bowl.
This sounds to me like the many situations that I run across every day. A homeowner decides to remodel their kitchen and recieves a few bids.
They can tell that one company is very proffesional, and has all of the necessary insurances on the company as well as his employees. And also carries the added protection of bonding. This company will fill out a full contract with scheduling and budget, including all of the materials that will be installed so the homeowner won't be suprised by the wrong backspash or anything. Possibly even a warrantee. BUT HIS PRICE IS THE MOST EXPENSIVE DUE TO HIS OPERATING COSTS.
The next company comes highly referred from a friend that has used them recently. This is a smaller company without as many perks, but that keeps their operating costs down allowing them to give a lower price than the first. Having a referral from a friend ensures that they perform quality work. THIER PRICE IS LOWER THAN THE FIRST.
Now the third guy comes in and hopefully at least he has liability insurance. He gives a bid astonishingly lower than the other two.
A lot of homeowners go with the cheapest installer figuring that they have high quality materials and that there is only one way to install them. Construction is not like auto mechanics. we don't just line up the parts and tighten the bolts to ensure proper alignment. This is craftsmanship, and takes great skill and pride to perform proper installations.
Also, I would like to mention that a lot of the hom depo stores and sears home installers are using subs that they have no training for as well as poor supervision due to thier corporate budget crunching. But their prices are no cheaper than a professional companys. Consumers fall prey to these companies due to the convenience of a one stop shop rather than receiving bids from real professionals.
I would contact a lawyer, and take many pictures to send to the installer with a lawyers note explaining that further action will be taken. or better yet, I would ask the lawyer if you could have another company properly install a new countertop and sink while forwarding the bill to the hack that installed your countertops improperly.
PEOPLE, ATTENTION, YOU GET WHAT YOU PAY FOR!!!!!!!!!!!!!!
To avoid this kind of situation, simply use your referrals from friends, or ask for some pics of previous work. Most of the compenies with all of their insuances and overhead carry them to take care of YOU in case of a problem. This raises their overhead, meaning that thier prices will reflect this fact.