If you don't need transmit capability, the SDRplay RSP1A has phenomenal receive performance for the price. If you do need to generate signals (and you understand your legal obligations), the Red Pitaya, LimeSDR and bladeRF are worthy alternatives to the HackRF.
The Red Pitaya is a particularly compelling alternative from a hardware hacker's perspective, because it does double duty as an extremely versatile measurement and data acquisition device.
The HackRF is a solid, if slightly dated SDR platform. There are plenty of better SDRs out there, but none of them are as ubiquitous and well documented/supported, particularly in the hobbyist space. And none of the better specs of other SDRs matter that much unless you need them, and you'd probably know if you do.
If you're just getting into SDR, I would just get a $20 RTL-SDR, and then move on to something like the HackRF or BladeRF later.
The Red Pitaya is a particularly compelling alternative from a hardware hacker's perspective, because it does double duty as an extremely versatile measurement and data acquisition device.