Hi Petersun,
I've been there 4 times and on all four visits as DBM mentioned I was faced with young sales clerks that didn't know anything about coins. The shop is rather small and they don't have a large selection. As far as price goes, it's all the same prices as the mint sells them for. I didn't see any mark up in the sets.
I did purchase my 2011 Boreal Set and a 2011 Specimen Set there but when I had asked for the Boreal Set the young guy at that time had no idea what I was talking about and told me that they don't carry those coins. I had to take him over to the display case and show him the set.
In my opinion the only way I'd go back is if I wanted a set right away and didn't want to wait the week for shipping. Otherwise I'd order straight from the mint. If your in downtown and don't mind getting frustrated with the lack of knowledge I guess it's worth a stop in, but I wouldn't plan a trip into downtown just to go to the store.