You might as well upgrade to keep current, been honest i havent noticed a huge increase in speed overall, i found the speed of current version fine, the significant difference i noticed was the speed increase in the stock message app when you try navigating to a long thread, previous version made me change to handcent beacause stock was so slow but useable now so will stick with stock.
I am waiting to see if it also cured the vanishing text message problem.
