Our Trust uses PSF - migrated off 12 separate FMS installations just before Christmas.
The PSF's cloud is a private cloud service so supports not only the accounting application, but also allows the storage of our finance team documents, shared files etc. They have just added budgeting, payroll and personnel and those are all going to be delivered through the one private cloud service which we see as being a huge benefit as everything else we looked at what actually different connections, support teams etc.
The user interface is either a Windows application delivered via RDP or a HTTPS connection to the browser based front end for Purchases, GRNs, Invoicing etc - so there is no software to be installed on any of the Trust's PCs - again ideal for us as we are geographically dispersed and our IT support is extremely limited due to all of our schools being primaries with no local IT support.
Your last point is valid - the decision does come down to meeting the financial requirements - we looked at HCSS, Sage, Civica and we also gave Capita/FMS a chance to bid (though I don't know why!). PSF was a clear choice for us on the Financial requirements and the technology deployment has meant that we have had no need to install anything or worry about access as our users can use the service from the school or even home!
We had concerns about support as we had read some of the negative postings, but so far we have had no issues - apart from the users having to get used to a "proper" accounting system after FMS - and the PSF support has been good.