FWIW, I asked a couple of heavy-duty outdoor Garmin GPSMAP 60CS users who upgraded to the 60CSx. They said you definitely CAN notice the faster sat acquisition speed with the SiRF-equipped 60CSx. Under all conditions. So, it's not just some manufacturer hype, it's a worthwhile feature to look for in a new purchase.

As for greater ability under covered conditions, that was a little less definite, but they "thought" it seemed better. Neither are deep canyon or rainforest etc. hikers...