Dave Ramsey has done a lot of good for a lot of people. His advocacy of getting people out of debt and onto the road for retirement is noble. I would highly advocate his tough love approach when it comes to reducing your spending and getting your debt under control.
I do have some issues with his philosophy when it comes to financial planners and investment returns. Both of these can cause very serious issues for you if you're not careful.
His belief that investments will return 12% into the future is very dangerous! One should use around 7% which is slightly conservative and is the very long term return of the stock market. When figuring future values it is better to be conservative and end up with too much money, rather than too little. Also, you need to look out for financial charlatans who claim they can get you more than this. They are out there, but they're very rare and like Buffett you don't know who they are until they've done it.
The other thing you need to be careful of is his advocacy of going with financial planners who work off of a commission, rather than a fee. Those financial planners will undoubtedly try to sell you financial products that you don't need, just to make a buck. When dealing with a planner who gets paid via a fee, much like a lawyer, ask up front what s/he thinks it will cost and make sure they stick to it. Shop around to find the one you trust the most and has the most reasonable fees. Cheapest doesn't mean the best value.