Most Helpful Guys
Friends only want the best for you, so there must be a reason or a motive for them doing this. Otherwise they're not your real friends. However, a friend may only have limited perspective, so you should talk it out with them or even your partner.
Ask your new partner to address some of the concerns if they are legit. Suggest that your friend meet your new partner sometime.
Most Helpful Girls
I'd ask why. If they are a friend I count on them to be open and honest with me and know that whatever they say isn't meant to be malicious or hurt my feelings. After all, they may know something about the guy that I don't. They may know ME better than myself, too, and can foresee problems arising before it happens.
Prepare yourself for the “I told you so” if it goes wrong. And if you truly believe in your relationship, prove them wrong.