The problem roto mentioned is a very common issue with Java applications accessing Oracle databases, ie the connections pile up and don't get closed when an application closes. They just sit there as 'inactive'. Maybe you're a better programmer than everyone else, but this occurs frequently.
About the sequence issue: Sybase has an 'identity' column; MySQL has an 'auto_increment' option, but Oracle only has a sequence. The sequence by itself does not in any way duplicate the identity/auto_increment featurs of the two previously mentioned databae engines. YOU actually have to create a trigger (a procedure) on a table to use the sequence for an auto_increment feature. That and sqlldr were 2 of the most annoying 'features' I had to learn when I started with Oracle. They are second-nature now, but these are much more difficult to learn and use than they need to be.
sqlplus: SUCKS! I use gqlplus; it has a recall command buffer and some editing capability. However, sqldeveloper is better (I cannot recommend Tora due to screen and data corruption issues I ran into). But I think many Oracle developers us 'TOAD'. Haven't used it myself, but it sounds like sqldeveloper.
jwhite