There are a couple of bugs that you will want to watch out for in 15.1:
- SB-Synonyms - don't set it to PUBLIC or anything that will load more than 500 of them, or you'll get an "out of memory" error and Toad will crash.
- SQL Recall not opening. Details and workaround here
Both are fixed in the current beta, which I recommend getting. The beta is nearly finalized at this point.