You will probably find very little criticism aimed at this little thing. It actually offers three devices in one: Midi controller with pads and knobs, step sequencer and USB midi to CV converter. All that for less than 100 euros is a small miracle. And you cannot see it in the build quality, BeatStep looks and feels very well made, and really solid.
The majority of BeatStep users, including me, has been drawn by its step sequencer with CV outs. However, I can see that most of people are perhaps a bit overenthusiastic when it comes to step sequencing over CV. BeatStep is one-channel sequencer and that means you can control only one signal, either pitch or filter or amp. Lot of times this is not enough. Step sequencing often benefits greatly from "accents" which are either built into sequencer as a function (XOX style) or there is separate channel for filter CV, amp CV, or ideally, both. That is why professional CV sequencers have three channels.
You can come around this by using a couple of (ideally three) BeatSteps in parallel. Maybe not very elegant solution, but still much cheaper than any other alternative. Because, if you want to go all the way into old school step sequencing, you will need something like Doepfer MAQ 16/3, or at least Dark Time (8 steps, two channels). And for that money you can buy handful of BeatSteps.
So, if you want to start exploring old school step sequencing, or to try connecting your pre-midi synth to the midi world, BeatStep is currently the best starting point by far. But, once you would want to add some nuance by controlling either the filter or ampllifier section, you will need to upgrade. For that reason only I am giving one star less than the maximum score.