@iris - The Garvey/Gevey SIM helped many bypass the 'locking' that AT&T had on their phones even AFTER the contract expired. I bought one for a friend for a locked iPhone.
Equitel isn't riding on Safaricom's network. A ThinSIM allows a single SIM phone to be used as a dual SIM phone. Equitel uses Airtel's infrastructure for data & voice. As phones become cheaper, the dual SIM phone will become cheaper too & the ThinSIM may be irrelevant. Apple has introduced an 'Apple SIM' which is not carrier dependent i.e. you can go to any carrier.
I have a dual SIM but I end up using Safaricom [& M-Pesa] more often since they have more tills. Plus I prefer the quality voice calls on Safaricom vs Airtel/Equitel. And using Safaricom for voice/data is cheaper than Equitel for me!
Data - My spend on Voice is less than 30% of what I spend on data. That's where Safaricom beats Airtel/Orange because within Nairobi I get 4G/LTE. I spend much more on data than voice. And Airtel has missed the boat on this. Equitel at most will be a money transfer service.
Greedy when others are fearful. Very fearful when others are greedy - to paraphrase Warren Buffett