I image one of the reasons for this being cold is because the op didn't include that this was a cashback deal in the title.
Yes and it's not £2.50 per month. It's £10 per month and you'd need to claim every cashback and for the company to remain solvent to get the £2.50 rate over 24 months. I've heard bad reviews of their cashback process and I'm not convinced of their sustainability. More reliable companies (all at some sort of risk) out there and deals come and go.
People really don't like cashback deals on this site, I'd imagine since the whole Phones4U collapse a lot of people lost out on cashback - that and the fact if Into Mobile Phones were to go into administration you'd be left with an underwhelming contract.
Be careful with this company. Good luck if you go with it.
At £10 pm it stacks up against GiffGaff and as long as you set reminders to send in the invoices the cashback refund shouldn't be a problem. The phone can be used as a backup or a standalone music player. Why cold?