I am interested to know which systems are most widely used in the US, UK & India.
Zenefits is top of mind, growing fast and operating all over the U.S., which is incredible because they're only a few years old. All of their HR services are free, like tracking employee PTO, changing 401K contribution amounts etc. etc., but Zenefits also employs a small army of insurance brokers. If you use Zenefits you can continue using your current insurance broker for employee health care policies, but they can offer you a quote as well. That's where a big chunk of their revenue comes from, which is fine. Btw the CEO still serves as the Zenefits administrator for the company, which I think is really cool, but that's coming from a product guy. Anyway I researched this topic last month, hope it helps.
Gregg M. Kennelly
In India you have one of the best flexible, agile HR system that fits in any device for HR management is ApHusys. You have a base version which is free module and pay per use for other modules as you go. This keeps budget low and effective if used for advanced modules.
I have personally implemented Ultimate Software in various companies and feel it is the best HRIS on the market. One platform can do payroll, on-boarding, sourcing, benefits, etc. Reasons for outperforming competition is because of the seamless integration and assistance during install. Have worked with Paycor, Paychex, Bamboo, etc. and nothing seems to compare. http://www.ultimatesoftware.com