sd cards and class ratings
The problem with sd cards, are that the rated class is often way off. They often perform much better.
For example, I have two kingston class 5 cards, that have read speeds at 12.5MB/sec, and one Sandisk class 4 with read speeds at >16MB/sec.
As comparison, I have a no-name class 6 that barely reads at 8MB/sec.
All three brand name cards also writes faster than the no name class 6. So why they are rated class 4 and not 6 is a mystery to me.
Ideally, we should have a thread where people posted the read/write speed of their sd crads, and included a link to where you bought it from. Mymemory.co.uk is a good place to get them from, in my expoerience. Does anyone know of online shops shipping worldwide that actually states the r/w speed of the cards? Or better yet, a table/wiki with this information?
To answer OPs question though: Class 2 will probaby be slow with Hero-roms or apps2sd. But you cn always test it and see how well it performs. I imagine reading speed is most important.