Customer support should not necessarily be priority 1, but be shared at a high level with quality of service and quality of the hardware and facilities...
You should always provide everything at the top-most level that your company can. It is a matter of getting things going, and providing a service that people will want to work with. Yes, it is great to have great customer support, but if you have customer support, but your entire DC goes down (like a fiber cut) then it makes it difficult for customers to recommend your services to anyone if they are having issues like that.
For many it is having a hosting provider who owns their own DC, and therefore can often offer 24/7 support.
I am talking from experience from my own personal point of view about what past and present customers have asked for.
Having a DC is one of the most important deciding factors and 24/7 live support is the second.
Agreed for some hosts 24/7 doesn't mean 24/7 live support, but those hosts would have to specify the live times of support.
For many it is having a hosting provider who owns their own DC, and therefore can often offer 24/7 support.
The thing is you can only "test" presales support as long as you're not a client, while the technical support is even more important.I will surely check the support service first.