So, here I am working on a 16-bit app in 2004.  I'm using Borland Delphi 1.0 for the task.  Overall, the project has gone very smoothly, but for some reason, the last couple of days on the project have been tough.  I think I narrowed it down to the fact that I'm way too familiar with the current, state of the art IDEs coming out of MS. 

Things that I miss while using Delphi 1:
Intellisense
Good code examples in the help
cool debugging tools (like floating your mouse pointer over a variable to see its value)
select a block of text and tab in or out
right-click on a procedure or function and view its definition

I'm sure there are more, but those are the biggest things that I miss.