I haven't personally tried this unit, but the write ups for either of the Arcam units seem to indicate a typical high quality and pleasing sound that Arcam built their reputation on. MiniBlink is more for your compact hifi system setup, the rBlink aimed more at the appreciative HiFi enthusiast. (They also do the Arcam irDAC II DAC (RRP of ~£400 but currently £275 at Richer Sounds) which swaps the Burr Brown for an ESS ES9016 Sabre DAC, plus handles multiple inputs.) I purchased Arcam's rDock for the iPod Classic way back when, and plugging it into the HiFi you wouldn't know it was an iPod creating all those fabulous sounds. I'm sure it's a similar story with the DAC the rBlink has at the heart of it design (Burr Brown PCM5102 24bit DAC) As you say, AptX takes care of the Bluetooth transmission, ensuring your compatible device and the rBlink communicate with minimal latency. Then all those zeros and ones are fed to the onboard DAC which then does the hard work of decoding your music. If you've already got a DAC of your own, then this rBlink or MiniBlink isn't for you.
I'm not an audiophile at all but the bottleneck on these Bluetooth receivers is the transmission codec right? In this case AptX if your phone supports it? Does the quality of the DAC help at all? you can get aptx receivers a fair bit cheaper?