Actually, tilling promotes weeds rather than suppressing them. The
soil is loaded with millions of weed seeds but only the top inch or
two get warm enough to germinate.

Actually, although I didn't say it very clearly the first time, I
agree with this.

Well, at least in the sense that tilling helps some weeds.

I'll maintain that it also will slow down others. It depends on
whether you are dealing with weed roots (perennial weeds which you
didn't pull up by the roots and the like), live weeds (in the case
where you are tilling after something has come up), what your soil
seed bank is like, and any number of other factors.

I tried a quick internet search, to see if one (or both) of us is
totally off base, but didn't find a whole lot very quickly. The most
entertaining (new to me, certainly) was about tilling at night:

http://findarticles.com/p/articles/m...43/ai_17840569

There is a technique named "stale seed bed" that discourages tilling
for this reason. I am experimenting with it this year and so far it
looks pretty encouraging.

Well, it discourages tilling at the same time as planting. Some
variations involve tilling, but some weeks (or more) before planting.
There seem to be many variants of this, from herbicides to flames to
hoeing. What they seem to have in common is that you *encourage* the
weeds to grow at some time *before* your crop is in, and then get rid
of them.

http://www.uvm.edu/vtvegandberry/fac...meweeding.html
http://www.newfarm.org/depts/readerm...7/0720_2.shtml

Most of the sources I found were more about direct-seeded crops than
transplants, though. The latter have a big head start on the weeds.