I use Moneysoft Payroll Manager and find it really easy - and the support is excellent, both by email and phone
I have staged with 2 different clients using this software - both have been linked with NEST and I must say, it's been pretty easy.
1 of the clients had a particularly complex situation, where they were going straight in on the 8% rate, but for each year that their employees had been employed, the employer was paying 0.5% of their contribution, up to a max of 2.5%, so again, this was a challenge, but very easy using Moneysoft. I had to phone Moneysoft to find out how I set this up - and they answered it straight away and made it so easy.
The only other problem I've had is not realising I had to have a different group set up for each 'set' of employees at this complex client at NEST. Once this was explained to me, and set up by NEST, Moneysoft recognised it all and uploaded it all in much the same way as the RTI report, with the same lovely clear explanations that it's been done.
I'm so glad I've stuck with Moneysoft for this task :-)