64 Bit CodeTeXShop has been converted to 64 bit code, and in the process a large number of warnings were eliminated and a large number of deprecated calls were replaced by modern equivalents. This conversion, incidentally, was done on Snow Leopard and the 64 bit code runs on that system (the Snow Leopard version has not been released).
Users might find glitches related to the 64 bit conversion. Please report problems and we'll try to fix them rapidly.
Users who compile TeXShop from source will still notice warning messages because certain warnings from the conversion process have not yet been systematically investigated.
ResumeTeXShop is constructed using object oriented programming and an Apple class library called Cocoa. One of the dreams of object oriented programming is that Apple could enhance the class libraries and then all programs would automatically get new features without even being recompiled. In Lion, that happens in a very magical way. If you quit a Lion program without closing all the windows, the next time you start the program, these windows will reappear exactly as you left them. The source code will be scrolled to its old spot, multiple documents will be opened, etc. If the system is shut down while programs are running, programs resume operation automatically when the machine is rebooted. Any program written with Cocoa using the NSDocument class automatically inherits this behavior.
In particular, TeXShop version 2 behaves this way without any new code, and certainly TeXShop version 3 inherits the behavior.
Occasionally you may want to Quit TeXShop without allowing it to open old windows the next time it runs. To do that, hold down the "Option" key and notice that the menu command "Quit TeXShop" has become "Quit TeXShop and Discard Windows." Select that item.
Similarly, you may wish to start TeXShop without loading old windows. To do that, hold down option-shift while starting the program.
These two "option" tricks work with all Lion programs.
The default resume command is not perfect. In the case of TeXShop, source windows are correctly scrolled to their old position, but preview windows are scrolled to the start of the file. Since syncTeX works, this is not a significant problem because users can sync from the source window to recover their old preview position. But there are other minor glitches. For instance, if you select a different engine in the source toolbar's pulldown menu, that engine will not be preserved on resume.
Apple documentation explains how to fix such glitches. Since "resume" works so well by default, I spent my time before Lion on other features, but the glitches will gradually disappear from TeXShop as it is upgraded over the next months.
Find BarTeXShop now has three options to handle Find and Replace. As in earlier versions, users can select the Apple Find Panel or the OgreKit Find Panel. There is now a third option, the Apple Find Bar. Select the desired option in TeXShop Preferences.
The Apple Find Bar looks more or less like it does in TextEdit and Safari. It appears at the top of the source window when needed, taking very little room. Apple crammed a lot of functionality in that small space, so it is worth taking time to explore the various options.
Note that finding additional matches is done by clicking the arrows in the Find Bar, and "Replace and Find" is done with a button in the bar. It is also possible to find more matches using apple-G and apple-shift-G, but these only work if you click first in the main source text to make it active.
Additional polish will be added to this option over time.