I just tried the stopwatch on my Clip Sport. If you switch modes with the stopwatch running,and play some music, when you return to the Sport screen, if you click resume, you can see the stopwatch has been running the whole time and continues to run while the music is playing. it works the same way on the Clip zip. The Clip zip doesn’t have a countdown timer though, which the Clip Sport has in addition to the stopwatch.
Keep in mind though that the Clip Sport doesn’t integrate internal memory with card memory. A playlist can have songs from one or the other, not both. The song limit is around 2,000 for the internal memory, and around 2,000 for card memory. If you have much less than 2,000 songs, then these limitations shouldn’t really affect you. Some get the 4GB Clip Sport, and a 16GB card, and have all their music on the card. For most people, if the fill a 32GB card with music, it would have well over 2,000 songs. The 2,000 file limits might be changed with future firmware updates from Sandisk.