Well, if the item isn't properly cleaned you can get infections.
Some women report they lose sensitivity and get to the point where they've inadvertently trained their bodies to only be able to orgasm with a vibe. I'd recommend switching it up. Use different settings in different positions, use your hands sometimes, have oral and PIV with your partner, etc.
Just like anything, moderation.
How vibes impact relationships depends. For women who cannot orgasm without a vibe, using one is necessary for her sexual satisfaction. Some men don't mind, some do. Of course, some woman will refuse partnered sex because they are meeting their own needs, so making sure to take into account your partners needs is important.
My wife is 65 and gets her orgasms by direct clitoral stimulation as most women do. Lots of guys do not know that most women do not get their orgasms from intercourse but rather the pressure put on a clitoris. That is why they all want longer penises when wider ones are better.
My wife has been using a vibrator for 45 years with no harm at all. However, since vibrators usually provide a more intense orgasm, women can end up needing them because sex with a man does not provide as much stimulation as they are used to. My wife has extremely intense orgsams from BOB, her Battery Operated Buddy. Only occasionally does an orgsam from oral sex come close to what she feels from BOB. I do not mind. For 30 years my bi wife and I shared the same bi girlfriend and as they got older they came to prefer using a vibrator. We still had sex but they usually finished with their vibrators. I kid my wife about BOB being the third in a threesome and my nemesis.
Health wise I am unaware of any health risks since I know women for a very long time who use them. The risk is that your clitoris can become desensitized so that you grow to prefer a vibrator.