I have two of the cabinets, the Micro VR Head, and the PF-350 head (I've used both with them). Originally I got the single stack for upright use, which the cabinets are great for (the head not so much). I used this setup for years with my upright gigs.
Recently I've been using the 2 cabinets with the PF-350 head for my rock band. The PF-350 is the same pre as the Micro VR, but with a bigger power amp. It gets good tone, but for my liking it doesn't move enough lows to make me happy in a loud rock band. If you're band is really loud, or you are used to feel of a ported bass cabinet - they may not be ideal. It really depends on what you plan on using them for.
Having said all of that, it is a great small setup. Tonally it's old school Ampeg, nice and punchy, cuts easily. Obviously not as rich as the real thing, but still very musical. Great with a P-bass running through it. The features of the head mate nicely with cabinets. The two were designed to work well together. Oh and uh, they look so damn cool.
In summary, it really depends on the scenario you are going to be using it in.