For me there are two main challenges. Being relatively new to the mixing/tracking end of things monitoring is very problematic. My studio monitors, at least for now, are roughly equivalent to 2 Campbell's Tomato Soup cans linked with twine. For this and other reasons I usually mix with Sennheiser 280 cans. Consequently, I've had some surprisingly good results and some scary weird results (I think I've sent you some of those).
The second is learning to make the most of what you have. I offer my services, such as they are, for free as a means of helping new faith-based artists accomplish something they wouldnt be able to otherwise. Hence the can-and-string approach. The challenge then becomes learning the myriad tips and tricks to make less-than-optimal gear sound at least acceptable. It's my belief that many of these limitations can be overcome just with good ears and patience (not to mention lots of free advice....right, Brett?)
I llok very much forward to learning some of what you all know.