This combo gets alot of love here on these forums, and for good reason.
Surprisingly loud for such a small package. I use this routinely for rehearsals from acoustic trios to jazz ensembles with horns to dual guitar rock outfits. I have even used it in performance situations when a larger rig was just not called for.
This amp has great tone shaping tools that help dial in to your instrument and the room. The four band eq is pretty handy on it's own but the VLE (Vintage Loudspeaker Emulation) and VPF (Variable Pre-Shape Filter) help with honing in the high end and midrange as well. Something you really have to try yourself to appreciate.
Some have said that Markbass is sterile but I disagree wholeheartedly. This thing reflects the liveliness of your instrument very well.
The small size and light weight has it's obvious advantages in transport and loading in and out. With my bass in a gigbag strapped to my shoulder I can carry this in one hand and still have another hand free for a six pack of IPA for a single trip into the rehearsal space.
After about 4-5 years with mine, it sounds as good as new and is holding up cosmetically except for the rubber on the carry handle which is starting to crumble a bit. The handle still seems sturdy but I will likely look to replace it soon.
The price of admission for a new CMD 121p is high, the used prices are a bit more palatable. Considering the reliability and superb functionality, this amp is well worth the cost if you can swing it.