What do you like best?
This was one of the top players back when "link building" was still a thing. In fact, many SEO experts complimented MyBlogGuest for its innovative approach in connecting guest bloggers with blogs at a time when most other "link building" companies were blatantly buying and selling links.
I appreciate what this site has meant historically, and I also don't appreciate Google's blanket bullying tactics towards them and their users in 2014 when many of their users were using the service legitimately. While Google would never admit it, I get the sense that it was the strong (and correct) stance of this company's founder to not kowtow to them that pushed them into developing algorithms like Penguin.
What do you dislike?
Truth be told, the quality of blogs and bloggers that are featured on this site are not the best. Had the service been a bit more fastidious about recruiting and curating top quality contributors and publishers, it might have gone a long way. But opening it up to everyone just invited blog publishers who were just looking for "filler" content and blog writers who were just looking to trade low quality content for a few links. Ultimately the service is only as good as the participants, and these are not the highest quality in the world.
Can you still get use out of the service? Yes, there are occasions when truly exceptional blogs or writers show up, but you need to dig for them. You're probably much better off doing it the old-fashioned way, identifying influencers yourself, and reaching out to them yourself.
Recommendations to others considering the product
Think very carefully about why you want to use a service like this. If it's "I want more links", chances are you're not approaching SEO the right way.
What business problems are you solving with the product? What benefits have you realized?
Years ago, the business need was to build more links. That ship has sailed. Today, the business need is to build high quality, relevant, and engaging content, and there's not much to be found here anymore.