Around 80% do not find the smooth handle slipper when wet, but 20% do. Some report that after feeling very slippery initially, it became less slippery, either because some finishing polish had worn off or they had learned how to hold it or both. If you brush your wet fingers over the alum block, you can get a secure grip.
As /u/almightywhacko indicates, the EJ uses standard threads, so you can swap handles, a great benefit of the three-piece design. These offer excellent handles for sale separately:
It seems likely that, with razors being sold unbundled (i.e., being able to buy the cap, the baseplate, and the handle all separately), we'll see more sources of the handles alone (since handles are easier to make than heads)---e.g., this one.
And, of course, you can use the handle from almost any three-piece razor---e.g., a Gillette Tech or NEW or whatever.
Now that we're starting to see razors being sold unbundled (head and handle sold separately, mix and match), it's likely that more handles will come onto the market---e.g., here's a good handle by Apollo, stainless steel, sold on Amazon.com.