During my trip to Sarajevo, before Vanessa arrived arrived, I took a day trip to Mostar by myself. It was mostly a success, although I ended up heading the wrong way from the station so went the scenic route to the main town.
I did manage to get to the main bridge area (from the opposite side than I had intended) and enjoyed a day walking around the small town. It is pretty small, and can be 'done' in a few hours. I was lucky with the weather as the sun come out, although I had decided to wear boots so that wasn't the most suitable footwear choice. It was also very difficult to walk around the main bridge area because my boots didn't have very good grip and the stones over the bridge are very smooth and slippery. The other areas were paved with round stones and it was quite uncomfortable to walk over.
I went into the small bridge museum which was interesting and ended with great views over the bridge and town from the top of the tower. Whilst I was at the top I also saw someone jumping off the bridge which was fun.
Most of the day I wandered in and out of the small tourist shops, I visited the Muslibegovic House, a 17th Century museum showing traditional ottoman style rooms of a noble family house. It was only a small complex and very rustic but a sweet little break from the city.
Mostar was definitely worth the visit from Sarajevo, and I'm sure if you stay for a day or two it's a nice chill out place although I couldn't see a whole lot of things to do in the town. I believe it is close to caves and waterfalls so also a good base for other day trips around the country.