It's a good case, quite sturdy and holds the DSi quite well with 2 elastic corner cross pieces. It has space (nets) for 3 games and holds a cleaning cloth well. It more is put in the back net - it can make zipping up the case harder,but that's likely the case with all DSi cases.
The reason for the 3 is because of the screen protector, there should be instructions as it is a little hard to peel off the backings, and the time you take means dust, fibre strands adhere to the back and cause bubbling of the protector - if it was easier, either through instructions or ease of taking off the backing then this would be fine.
The other is the packing of the larger screen protector, it's packaged into a small space thus bunches up and is bent when you take it out, bent to the fact that you can't use it top screen). Now I contacted Snakebyte, but customer service these days is lacking and they said they couldn't send out screen protector. So are not too bothered.
So it's a 4 for the case (as it does the job - so maybe a 4.5), 2 for Snakebyte customer service ... so 3 overall.