Here in New Zealand essentially every start-up uses Xero - a SaaS accounting system that works extremely well and now has over 600k paying customers.
It means one set of data, permanently in the cloud, and a host of integrations to other players.
Founders open up access at different levels - we can give read-only to directors and some investors, advisor-level access to accountants and bookkeepers and so forth.
Frankly it's part of the NZ advantage right now (120000 or so of those customers are here) - we seem to be spawning a large series of smart, low cost B2SMB SaaS businesses, who are not just following Xero's own path, but also using the tool to improve the way they do business.
Not everyone thinks it's a good thing. For instance, with Ledger, you don't have to be a customer. It's available for free. Anything that works good without SaaS is better done without SaaS.