Due to a long-term subway service interruption, I have begun commuting by bike

On the upside it is invigorating. On the downside it is exhausting.

On the upside it is efficient exercise with no gym costs. On the downside you compete with cars. 

On the upside it is faster than public transportation. On the downside you cannot read. 

On the upside you see the world differently. On the downside it could rain. 

On the upside it demands focus and concentration. On the downside it requires focus and concentration.