We are Xero-certified partners and provide services to a number of clients who use it. I think it is a great option for clients who suit their Xero Ledger product – which is a very low-cost package ($3 USD per month) meant for very small clients. This particular package is only available from a Xero-certified partner.
Companies that require multi-currency support will need to opt for their most expensive package ($40 USD) per month. If the monthly cost is trivial for your company, this is a great package for those who require multi-currency support.
Xero and Quickbooks both work hard to get CPAs and bookkeeping firms to recommend their software and offer discounts to their accounting partners to offer their software to clients.
It seems to us that Xero is a favorite with technology startups. By contrast, Quickbooks is more popular generally.