The kind of Customization done by us, Migration of data from various data-formats (including proprietary formats), has given excellent experience to our team's capabilities.
Setting up a central server for ICAR 33 partners, helped us create a new example of Koha's implementation that resulted in huge saving of infrastructure cost to our client.

All this has been possible, solely based on our intention to create examples that can actually surprise our clients about the wonderful possibilities with Koha and Open source, while remaining affordable and without compromising on features.

Based on our experience, we would like to share our suggestions for choosing a vendor :

Being a crucial decision that needs to be taken with plenty of care, during the selection process, you need to see, not just the capability and team profile, experience and client list, but also the intention of the vendor.
While it may be true that people do business for money, when some of them do business just for money at any cost, they end-up in negativity of life and, in the process, take you, as their client, also in the same negativity.
There are examples when the vendor goes on offering just about everything you wish for without increasing prices, just to get the work order from you. Usually this boomerangs on you, with a badly done job.
There are examples when the vendor gives you a very low price, masking the deliverables. Later, when you realize the missing aspects of implementation, you are asked for extra money for those "extras". This brings you to vendor-lock position and you end up paying much more that the initially "higher cost vendor/s".
Intentions are the most important aspects to be checked. When the intent is positive, the other important things like capability and experience get clarified in a better way.
Another aspect, that can play positive role in creating and maintaining a long term positive relationship with your vendor, is to ensure from your side that your vendor earns profits from your your business. Reasonable profits, even when they are transparently known to both sides, are an excellent tool to create a positive relationship.
Having ourselves resolved many issues of "failed relationships with other vendors", we understand the pain that you can go through by selecting a wrong vendor, and hence this sharing of experience.