Absolutely from a teaching perspective, though keep in mind an academic general internist salary isn't going to necessarily wow you. Keep in mind that many academic IM doctors "specialize" in a non-formal manner, e.g. I know people who "specialize" in the primary care of transgender patients, of athletes, or of the homeless - it's not like they did fellowships for that. If you are interested in QI or healthcare delivery, you don't necessarily need a fellowship for research. If you want a significant portion of your academic effort to come from research, that is a bit more complex, but again, a fellowship won't necessarily make it more simple.