single member llc - separate business & personal?
Should a single member llc use a separate company file for business and personal finances?
Should a single member llc use a separate company file for business and personal finances?

That is the way I do it. I tried using Quicken for the Personal but found it easier to use QB with two separate files. Some people will find Quicken more useful if they have do stock trading, etc. I am assuming you already have separate business and personal checking accounts, CC, etc. as it essential that you separate personal and business finances AS MUCH AS POSSIBLE. However, you then have to merge the data to prepare your tax return. I haven't figured out an easy way to do that yet.
Will
@wm
why would you have to merge data for taxes?
Sole-P (single member llc) reports business income and expenses on schedule C
personal deductions are on schedule A, with personal income on the 1040 and / or schedule D (stocks)