Not the fastest card on the planet, so it takes a while to fill up. But as its designed for mobile devices speed isn't such an issue when away from the computer. Works well in my PSP with an adapter too.
I've also had two of the 8GB versions for longer, which have been absolutely fine.
By far the cheapest around so I would not hesistate to recommend.
The cheapest Sandisk 16gb microsd card I could find was £60, but most were more expensive. I had also read that the Sandisk 16gb memory card has some problems with data corruption on the Nokia 5800xm. The play.com 16gb card has no such problem.
This memory card is a must buy for any media fanatic like me!