We are with NEST, not had any issues so far.
As said before I can't imagine why anyone wouldn't want to be part of something only for the reason you get the X amount contributions from your employer and your contributions get tax relief.
TBF, we didn't look too much into it when we set it up as they did seem much of a muchness. What bad reviews has it had? I can't imagine any of the auto enrolment ones have been going long enough to give any feedback regarding how they mature.
I'm purely looking at mine as a glorified savings account, I don't expect any huge return maybe 1-2% over what was put in it.
If a pension scheme makes on average 1-2% after charges it is diabolical and avoid putting your own personal money in. The only time a pension scheme should be making 1-2% is moving the money into a very low risk fund which is advisable in the last years to protect yourself from volatile markets before you retire.