Is everyone using MDF for this table?
I was thinking of aluminum and anodizing it.
Does anyone forsee any problems with this?

Well your biggest problem is going to be that the plan dimensions are for 3/4" thick MDF so you will have to take that into account when using a thinner material - I assume you're not using 3/4" aluminum!

There are probably other CNC designs that are better suited for aluminum, I've seen quite a few that use the square AL tubes with t-channels, some posted on this site. I suppose your biggest hurdle would be finding open source plans for such a design.

Another option for JGRO machines is to do the entire thing out of HDPE which machines incredibly easily and is a lot lessy messy than MDF, plus you don't have to use superglue and re-tap each hole as with the MDF. The cost for that much HDPE is what makes it prohibitive however.