How important are transports?

Probably depends on the specific innards of the DAC you are using. Per a musical fidelity dac review in stereophile, that company's designer (Antony Michalson or something like that)says they reclock the bit stream in the DAC, and so which particular transport or cd player with digital output you use doesn't make diddly for difference.
A DAC which does not reclock might be much more sensitive to variations in timing from a less than perfect signal source.
There are a lot of great used cd players with digital outputs, my suspicion is that a great cd player probably does not have poor bitstream timing and tends to be priced a lot more competitively than a transport. Other thing is it is handy to be able to swap back and forth between the cd player output and the dac output when evaluating your system or when your dac is on the fritz.

1's and 0's are one's and zero's if they are all there. I own the MF TriVista Dac and the transport made all the difference in the world.

Here's what I know: the $30 CD Drive in my computer can read most CDs (except those that are heavily scratched) PERFECTLY (tested via checksums during the ripping process) at speeds up to 52x normal playback speed. If you don't think your audio-quality CD drive can read CDs at 1x playback speed, or some ridiculous liquid you apply to the surface of the CD will somehow make these perfectly read bits sound better, I've got some swamp land in Florida you should definitely think about investing in. :)

It is all about the DAC.

I can not disagree more with Scrith's comments. My findings are that the transport is at least as important as the DAC. It's not about the ones and zeroes, it's about the timing of the ones and zeroes. This is jitter. I updated from a Theta Data Basic to a Basic II and the difference was outstanding. Half a dozen other transports have fed my DAC (Theta Gen Va Balanced) over the past few years and no two have sounded the same. Disclaimer: I bought land, and live, in Florida. So what do I know?

Years ago I was auditioning speakers in my home, the dealer offered a Meridan 200 transport, I already had the meridian 263 dac driven by a Rotel 845 (i think ) The transport made a bigger difference than the speakers! I ended up buying the transport instead of speakers and still have it! FWIW.