I can't believe how many cases out there are just crawling with metal splinters, rough edges and razor sharp corners just waiting to cause me grief. Make sure your case has a nice smooth finish to it. Nothing can ruin your computer tinkering fun like a slice in the palm. And also, double check to make sure it's not made out of aluminum foil. Cheap metal is not better than cheap plastic.
Cases come in varying forms of screwlessness .
Most screwless cases are only screwless with regards to the case coverings. But even at that, the screwless case can make tweaking and upgrading almost joyful in process. It's also great when you consider how many times you may need to make finely-tuned fan and temperature adjustments when embarking on your overclocking quest. But the screwless case is not always a sure win. However, some screwless cases are just plain cheap, and you should inspect the quality of any flexible plastic parts closely.