My biggest complaint is the tool tray, for two reasons:
1.  There's a finite number of items.  Since I keep antibacterial gel and fruit etc for when my peeps get sick, it can take two or three trips to buy all four food groups for them.  I wish it had some kind of scrolling feature.
2.  You can only buy one of anything at any given time.  I don't mind so much when it comes to workbooks, but if you buy ANY female (or male) outfit, you're not allowed to buy another.  This really irritates me as - given the way things change in the store - I tend to buy for peeps in advance.  I wish there was some way of storing the outfits you'd bought, like putting them in the closet or something, or if that didn't work, having a Clothing tooltray similar to the Decoration one 
