One tip, on my commuter I use MTB clips and shoes, on my road bike I use look pedals and road shoes. I find it to be safer/easier to commute on MTB pedals in traffic.
The soreness goes away with time, my recommendation is to gradually add miles, but a good seat is paramount. I took a week of recently (product of weekend trip and a cold) and my first ride was 75 miler. Boy was I hurting at the halfway point! Just one week out of the saddle and my "sit bones" had gotten soft.