Actually it sounded pretty good. As the soloist you get to set the tempo and, although I normally hear it played at a faster tempo it sounds very good at the slow tempo. In fact at the slow tempo it sets a very different mood and dimension than when its played fast.

To learn to play fast you have to, well, ... play fast. Break it up into small sections or work on it a measure at a time and play the measures as fast as you can. Then when you slow it down even a little bit it will seem easier.

DanielB said
Don't worry about speed at first.  Speed is probably the easiest thing to get from just practising a piece. 

Go for playing with a good tone and feel.  Speed will come pretty much automatically over a bit of time.  In fact, you sometimes end up having to slow a piece back down somewhat to make it sound right, after you get it faster. LOL

But with slowness, one way to get the transitions and embellishments better on a piece are to slow it way down and work it that way for a few days.  Then when you let it go back up the the tempo you want it at, your fingers can know just what to do. 

What you are saying is absolutely true. One think I picked up playing in the orchestra is that it is often more difficult to play pieces that were meant to be played slow slow. All too often musicians tend to gravitate towards playing too fast and it can ruin the feel that the composer intended. Likewise, playing soft can be difficult. One of the biggest complaints our conductor has is that when a composer calls for a passage of music to be played piano we still tend to play too loud and have to really force ourselves to play softly.