yes back in the early days, in pc's you could get even better performance with compressing because HD's where really slow compared to the processor.

But with the way flash works.. i dont know if this is really a gain..

For example reading 1KB will result in a read of 1 Page (mostly 4KB)

and writing is especially with not so performing i/o controllers is done in Blocks and those are X number of pages of total sometimes 512KB at total.

So to write a 1KB block 512KB needs to be read in. 1KB updated in that block and then 512KB written again.

But this all depends on what kind of flash controller is in the N900...
But i cant believe that with flash we really gain much in read speed and write speed is really a bit slower..