I think guns need both re-balancing and new prices - for example, once I got the DM24 all the other guns were paled in comparison. Rate of fire differences between the primary weapons would be nice too.
If you buy anything permanently, make sure not to upgrade it, it will remove the permanent of the item. And don't bother selling half the items - You can't, it just freezes at "selling item..."
Some sort of shop that is scaled to what dungeon level you are on would be a nice, giving a little more incentive once you have all the titles you want.
Every time I finish a level, I get massive overlaying of the same music, which nearly broke my speakers -.-'
Is there something wrong with the music playback or something? It sounds like the loop feature is broken to me.
It only takes one hit, but the hitting system is far from perfect