Revision A means it's the first model of new hardware / or new design. Sometimes they exhibit flaws cause they are the first model. I had rev a powerbook 12" g4 and it eventually died completely. it lasted a good while though and went threw hell. Had to ship it back a few times. But typically revision a's do have more problems then later revisions.
The current MacBook Pro models are way beyond Revision A. You can buy one and expect them to be fine. I have a Unibody MacBook that performs, even though considered a Rev A, perfectly. No problems and my battery hasn't even started to wither/die (it has 280 load cycles and 13 months and is at 4126mAh)
True, but if they were to make substantial upgrades to the screen res, and switch to a new line of cpus and graphics card, then I'd consider it a risk more similar to a rev A product. Anything more than a speed bump and harddrive upgrade makes it more rev A than rev D.
If it's just a speed bump in January, then there should be no worries.
Also, I can't blame the OP for being confused by the term rev A. A revision would imply thst it has been fixed or improved somehow. Technically, what we call a rev B product is actually the first revised version of that product, and should be considered rev A.