Moving from View 5.0-- Which version is most stable/best performing?

All,

I have a customer (financial institution) that has gone 100% VDI at all banking branches. We started building this two years ago on ESXi/View 5.0.1 -- Now, with so many versions out and View 6 incoming, any advice on which version to upgrade to? There are only two key items that matter for the customer:

* Reliability

* Performance

They are not interested in any major features but just want good old fashioned desktop pools. Any advice?

Thanks in advance!