if the internal storage is your main problem, then there are ways to solve almost completely,
but that would require you to root + s-off your phone
you need a non-Sense ROM that has A2SD+ and also flash a different hboot for larger internal storage (/data) partition
but the end result is totally worth it.
currently I'm on MIUI ROM with N1 table hboot and applied the "cmtd storage solution for MIUI",
now I have total of 286mb of internal storage, with 199mb left after 83 user apps installed
just an example to give you an idea what you will get after going through all the trouble of rooting + s-off

the link is provided on the first page,
but anyway here is the link
what kind of problem?
I'm using whatsapp on miui, no problem so far

---

Added on February 17, 2011, 7:14 pm

Firerat script does not move dalvik to cache partition. If you see on cm7,  it is due to cm7 built in script