Probably the biggest issue was early on some of the 2015 cars had bearing issues that caused knocking and led to warranty engine replacements. See the engine knock test to put your mind at ease:
Other than that, I can't think of any particular serious issue. Members have reported a few random and recurring smaller issues in this thread:
Thread: Micra warranty repairs -- have you had any done? Or trouble-free so far?
The Versa/Note 1.6L drivetrains are identical mechanically, except where they use the CVT, obviously.
I advise friends & family members to stay away from CVT's if they're planning to keep a vehicle past the warranty period. They're super-efficient, but just not as durable as the old school slushboxes (or manuals, obviously).
IF we go the compact car route the other contenders were the Mirage and Spark which are a turn off for me mechanically. CVT in Spark and Mirage doesn't seem to have been well received.
Let us know what you end up doing!
View my fuel log 2015 Micra S manual: 5.0 L/100 km ... 56.5 mpg (Imp) ... 20.0 km/L ... 47.0 mpg (US) ...