It is a good deal if you really need unlimited data. If this tells you anything about T-Mobile's coverage, I just left t-mobile 3 weeks ago for Cricket because I was tired of having lousy coverage any time I left the city. I decided coverage was more important to me than having unlimited data and I'm very happy I made the switch to Cricket. Your priorities may be different, though. The nice thing about cricket is that you can change plans mid-month if it looks like you will be running out of high-speed data. I've got five lines on Cricket, each with 2.5 GB for $100/month. I'll up my plan to the 5gb plan on my lime only for an extra $10 or up to the 10gb plan for an extra $20.
One other thing that soured my experience with T-Mobile was how they screwed me out of my unlimited data stash and started putting a cap on it. So, watch the fine print with those guys. They are constantly adding promotions and taking them away retroactively without your permission. They have also said that their unlimited data plans will not be forever. I won't get into it too much, but I just can't trust them anymore after my experiences with their customer no-service. That and the way they treat their employees...