Has anyone done a cost segregation? I'm curious if beneficial?

 This is a very broad question. Cost segregation will accelerate depreciation. That means more expenses in early years and less in later years. You are not getting more expenses, just shifting when you can claim them. There is three things to consider:

1. Is the cost of the study worth the benefit. It likely makes sense on a an apartment building, but a single family or small multifamily, it may not.

2. In your situation is it better to have the tax write off now versus in the future? If you are in a low tax bracket right now, it may make less sense than if you are in a high tax bracket.

3. Most importantly, can you benefit from the accelerated expenses? If your expectation is to take passive loss against W2 income, then you need to either qualify within the income level or qualify as a real estate professional. There is no reason to accelerate if you can't benefit from the tax loss. 

Also be aware there are algorithm based studies and engineered studies. The engineered studies involve someone coming on site and doing a full study. These are the gold standard for meeting IRS criteria, but they cost more due to the costs of the company performing them. These cost thousands of dollars. Algorithm based is when you plug numbers into a computer program and it generates the report. Nobody comes on site or looks at your specific property. These cost hundreds, but are more likely to be questioned by the IRS in an audit. Some of the companies performing algorithm based will stand behind them and even do a full engineered study if you are audited. 

Bottom line, make sure there is clear benefit because there is expense involved in this.