Adding your brand name to your meta description shouldn't cause any problems unless you are short on space for your primary keywords or unable to keep your meta D's under 160(ish) characters. I regularly add them to my clients meta's because I want as much brand exposure as possible. I want them to see my brand every-time they search. So if they modify the search query and the result change but I still have a top placement... they are getting another look at the brand without even clicking through to the site yet. It's likely a small impact, but if you have the space in your Meta's -- I'd say go for it.
