i compared alot the last couple weeks, and i ended up going with the 7422gx, and am very happy i did.
better display (brighter and wider), better video card, more power, a full ghz memory, dual layer dvd burner... much better for dvd/apps.. and it plays games very well for a laptop.
the 4540 will have a bit better battery life, but the 7422 runs about 2.5 hours full charge, so that's fine for me, and the weight is no worse than my previous compaq, so that's not really an issue..
the 4540 is about $200 less tho if budget is important..