Mark has been my tax preparer for over 20 years. The first time I met with him, he reviewed a past year return, pointed to an income item, and said: "The IRS will require tax be paid on this." That return had been prepared by a pricey firm with very nice offices, and I (mistakenly) believed that this meant they were likely more knowledgeable than Mark. I was wrong, and Mark was right about the back taxes owed.
Since then, there have been several times where the "enrolled agent" part of Mark's expertise has come in handy, including a time when both California and Minnesota (where I now live) demanded tax on the same Roth IRA conversion. I recommend Mark highly; he has saved me money and a lot of worry.