Timing has worked well for me so I'm a hieratic. You can't buy a good deal if you don't have the cash
What is a hieratic? Is that a new investment term for folks that are into market timing?
On the second point you don't need to hold cash to buy "a good deal":
1. if you have a high savings rate you can divert a substantial amount of $$ at a specific investment opportunity on short notice. If you need to move fast you can buy on margin and pay it off in a week or two when you are paid.
2. if you have a diversified portfolio you can sell other investments and buy what you feel is a good deal as you rebalance towards your target asset allocation. In tax sheltered accounts there won't be any capital gains to deal with.
-- Vik