An Xword without a theme is like a meal without carbs: it's a meal all right, but it's unsatisying. I guess they all can't be gems, but this puzzle is more like paste. For example:
- "Unstoppable" for ONAROLL is not very good. Someone on a roll is in fact stoppable; he just hasn't yet been stopped.
- "Polar outburst" for BRR is also weak. Brr is a sound suggesting cold; it is not an outburst, which is loud and demands attention.
- And I would not cross DUGONGS with VULGARIA at the u's because they are two rare words. Unless the aim is to make the puzzle difficult, it seems a bit unsporting.
- I also did not like "1 for H, e.g." for ATNO because no one really uses that abbreviation. The clue would better have been "___ time...."
On the plus side, "Common yuletide mail"
for CATALOG and "'Gimme _____!'..."
for ANO [better than the typical "year in Mexico"] are clever, and the grid is challenging to construct.