I have five at the moment, and a few more in the pipeline. The only problem I've found is that it takes a long time to heal (nothing new there

) and sometimes the scar tissue raises up for no apparent reason, so I can actually "feel" my tattoos like they're in braille

. My tattooist has never come across this before and thinks it's just because all my scar tissue is odd (my tattoos are all between four years and eighteen months old, so not particularly recent).
As with anything else, be careful, go to a reputable tattooist and make sure that you take good care while it is healing. I wash mine three - four times a day in warm, soapy water, pat dry with a soft towel and slather Bepanthen cream on them. So far, I've never had a single issue.