Well, that's what I've tried to find out.  So what I did was to take all of the high school positions players drafted in the top 15 picks of the draft going back to 1995 who played in the year they were drafted (holdouts eliminated a fair number of players).

Snider played in the Appalachian League this year.  The Appy league is similar to the Pioneer League, Gulf Coast League and Arizona League.  All players who played primarily in that league are included below.

Snider slides in right after Fielder, Butler, and Mauer.  That's not bad company to be in.  Also consider that before his wrist injury that cut short his season Snider was still improving his rate numbers (his August OPS was 1.248 in 86 PAs).

Looking at Snider compared to the top three, all three players ahead of him had much higher batting averages.  Snider's power ranks in the middle with Fielder well ahead and Mauer well behind.

Most similar to Snider's batting line is Josh Hamilton, the #1 pick in 1999.  Hopefully, for Snider, the comparison ends there as Hamilton's career was derailed by personal issues.

After the first few players on the list it really becomes hit or miss (or inconclusive for some of the more recent picks).  Some players had strong debuts and it wasn't a sign of things to come.  Others had slow starts, but it didn't stop them from becoming top prospects.

Over the same time period there were also several players who played at a higher level than the rookie leagues.

Interestingly, no one has played a majority of their games above rookie ball since Ryan Christianson in 1999.  The Jays were fairly aggressive with Lopez and Wells and both had great debuts.  The A's were exceptionally aggressive with Chavez - they threw him right into High A ball.  But like the other list above I don't think you can draw anything conclusive from this.  Wells and Chavez became All Star level players and the rest go from decent to washouts.

So based on this what can be expected of Travis Snider?  I'm not sure anything can be expected, but it's certainly a better sign to be at the top of the list than the bottom of the list.  Snider is off to a good start, but that doesn't guarantee anything.  But you already knew that.