The RX sensitivity is trash on the hackrf, you'll want an lna for every band you work it.
You can tx with it but being half duplex makes it really limited. Fun to play with but an sdrplay will likely bring you more bang for your buck. No tx but unless your a researcher or a ham doing odd modulation experiments you won't need it.
I found the sensitivity to be good on HF, BCB, FM, just as good as any dongle-SDR. Good on the low and high VHF public service bands too. Not that good up on 400 MHz. Agree that it is good for experimentation.