I have a Mini and I regularly commute with it. In fact I commuted with it for a few weeks every day. My commute is 57km round trip. If the bike fits your body while you are sitting comfortable on it, then the rest is a non-issue. Fit dominates all.

I am not limited to those distances either. Im am completely sure that I can spend literally whole days riding it with no 'effects' that I wouldn't get on my other bikes. In fact I am going on a 3 week holiday overseas and to stay in shape for a big ride in January, I am taking my Mini along and will train on it doing multi-hour rides.

Just one observation, my Mini is 5-10% slower than my other bikes, at this stage I am still not sure why this is so. I think tyres are a major reason. But it's not bothering me, it wasn't designed for speed.

You must be able to bear stares, smiles, boys calling out 'cool bike!' and be ready with explanations that 'no, the small wheels don't make it harder to pedal. It makes it more fun.'

IMHO YMMV.