As the chart above shows, monthly changes in private sector jobs can be, and typically are, quite volatile. You can't draw strong inferences from one month's numbers.
The chart above looks at the rate of change in private sector jobs over the past six and twelve months. This has been roughly 1.8% since last summer, and that is a relatively slow pace even for this relatively tepid recovery. We'd have to see a few more months of job gains like January's before getting excited. I'm not saying this won't happen, just that it's premature to declare that the pace of economic growth has accelerated.
The growth of the labor force has been unusually weak for most of this recovery, but it has been improving somewhat on the margin for the past year or so. I'd expect this to continue.
Part-time employment has been fairly steady for the past seven years or so, and it has declined to a relatively low level compared to the total employment, as the chart above shows. This is the pattern which has prevailed in almost all modern recoveries. Nothing remarkable.