I worked on a startup with a mogul-type celebrity and it was a real asset in getting over growth hurdles. For instance, the access to other companies and people that can help you is like nothing I have ever experienced before. Celebrity founders can also be like steroids for your brand, meaning they have already built a user base that will try anything they recommend and support any new product they launch. The network effect is real and can be helpful in PR and partnerships.
On the other hand, while celebrities can amplify growth around launch events through press and social media, you might quickly hit a ceiling in a startup, no matter how famous they are. That's where the hard work of starting something new and of high-value comes in. You have to make sure you have a great, value-add product that can build on that momentum. Otherwise, celebrities will give you short 15-minute windows in the spotlight that could go wasted.
I think of it like this. Celebrity or not, you will face most of the same challenges other startups face, but you have an unusual user acquisition asset. Use it like any other high-value acquisition channel and make sure you deliver value on the other end.
Success in using celebrities to drive growth will be heavily dependent on the industry you operate in and the makeup of your users. I was in media, so the celebrity angle was a real advantage. The music industry might also benefit.
I don't have experience in celebrity endorsements, but based on my experience, if I had to pay a celebrity for their likeness and leveraged them primarily for acquisition, there might be a better use of my dollar elsewhere.