As we get older, regional accents work against us more and more. I'm born and bred NY suburbs, which means a mild NY accent that has diminished over time. I think it's always a good idea to moderate one's regional accent. Having said that, my girlfriend loves my pronunciation of water (wauter).
In most cases, a strong regional accent makes one appear uneducated or "slow" to those who don't have that accent. It's just human wiring. One can increase his appeal by moderating his accent and learning to enunciate more clearly.