The install went great, I had not problems (but damn did it take some time).
It will not reformat your drive so all your applications and documents should still be there. But, if you do an OS upgrade without having proper backups only God can help if something goes wrong.
I do have one problem that I have ran into. I am using a program called Ghostread, but every time I try to do something to change the program it crashes on me. I have tried updating with zero success. I have e-mailed support but they take 2 weeks to get back to me.
No this program was not bought from the App Store, I paid and downloaded it from there webpage.
This is the "Problem Details and System Configuration" from the problem report. I have no idea what it says, but I hope it helps you.
Process: GhostReader [179]
Path: /Applications/GhostReader.app/Contents/MacOS/GhostReader
Identifier: com.convenienceware.GhostReader
Version: GhostReader version 1.6.5 (1.6.5)
Code Type: X86 (Native)
Parent Process: launchd [132]
Date/Time: 2011-07-20 16:18:08.285 -0700
OS Version: Mac OS X 10.7 (11A511)
Report Version: 9
Interval Since Last Report: 14387 sec
Crashes Since Last Report: 6
Per-App Interval Since Last Report: 2516 sec
Per-App Crashes Since Last Report:
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Application Specific Information:
objc[179]: garbage collection is OFF
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 com.apple.CoreFoundation 0x9b6baf79 CFRelease + 25
1 com.convenienceware.GhostReader 0x000384be TextParrotPrefsWindow::Build1VoiceMenu(OpaqueControlRef*, unsigned long) + 658
2 com.convenienceware.GhostReader 0x000394b7 TextParrotPrefsWindow::BuildAllVoiceMenus() + 53
3 com.convenienceware.GhostReader 0x00039742 TextParrotPrefsWindow::SetControlsToValues() + 634
4 com.convenienceware.GhostReader 0x00038b78 TextParrotPrefsWindow::InitializePrefsWindow() + 202
5 com.convenienceware.GhostReader 0x00038ba5 TextParrotPrefsWindow:😛refsWindowCommandHandler(long) + 33
6 com.convenienceware.GhostReader 0x00036da4 TextParrotApp::KSApplicationEventHandler(OpaqueEventHandlerCallRef*, OpaqueEventRef*, void*) + 2454
7 com.apple.HIToolbox 0x936eae54 _InvokeEventHandlerUPP(OpaqueEventHandlerCallRef*, OpaqueEventRef*, void*, long (*)(OpaqueEventHandlerCallRef*, OpaqueEventRef*, void*)) + 36
8 com.apple.HIToolbox 0x9356682b _ZL23DispatchEventToHandlersP14EventTargetRecP14OpaqueEventRefP14HandlerCallRec + 1602
9 com.apple.HIToolbox 0x93565ca8 _ZL30SendEventToEventTargetInternalP14OpaqueEventRefP20OpaqueEventTargetRefP14HandlerCallRec + 482
10 com.apple.HIToolbox 0x9357aac9 SendEventToEventTarget + 76
11 com.apple.HIToolbox 0x936eb318 _ZL18SendHICommandEventmPK9HICommandmmhPKvP20OpaqueEventTargetRefS5_PP14OpaqueEventRef + 482
12 com.apple.HIToolbox 0x936eb382 SendMenuCommandWithContextAndModifiers + 70
13 com.apple.HIToolbox 0x937557ef SendMenuItemSelectedEvent + 275
14 com.apple.HIToolbox 0x935b7598 _ZL19FinishMenuSelectionP13SelectionDataP10MenuResultS2_ + 129
15 com.apple.HIToolbox 0x937466c4 _ZL14MenuSelectCoreP8MenuData5PointdmPP13OpaqueMenuRefPt + 608
16 com.apple.HIToolbox 0x937467c4 MenuSelect + 183
17 com.apple.HIToolbox 0x936eee9d HIMenuBar::HandleMouseEvent(OpaqueEventRef*) + 89
18 com.apple.HIToolbox 0x936eee3a HIMenuBar::HandleEvent(OpaqueEventHandlerCallRef*, OpaqueEventRef*) + 158
19 com.apple.HIToolbox 0x93566e77 HIObject::EventHook(OpaqueEventHandlerCallRef*, OpaqueEventRef*, void*) + 163
20 com.apple.HIToolbox 0x936eae54 _InvokeEventHandlerUPP(OpaqueEventHandlerCallRef*, OpaqueEventRef*, void*, long (*)(OpaqueEventHandlerCallRef*, OpaqueEventRef*, void*)) + 36
21 com.apple.HIToolbox 0x9356682b _ZL23DispatchEventToHandlersP14EventTargetRecP14OpaqueEventRefP14HandlerCallRec + 1602
22 com.apple.HIToolbox 0x93565ca8 _ZL30SendEventToEventTargetInternalP14OpaqueEventRefP20OpaqueEventTargetRefP14HandlerCallRec + 482
23 com.apple.HIToolbox 0x9357aac9 SendEventToEventTarget + 76
24 com.apple.HIToolbox 0x9357b27f _ZL29ToolboxEventDispatcherHandlerP25OpaqueEventHandlerCallRefP14OpaqueEventRefPv + 1969
25 com.apple.HIToolbox 0x93566ce6 _ZL23DispatchEventToHandlersP14EventTargetRecP14OpaqueEventRefP14HandlerCallRec + 2813
26 com.apple.HIToolbox 0x93565ca8 _ZL30SendEventToEventTargetInternalP14OpaqueEventRefP20OpaqueEventTargetRefP14HandlerCallRec + 482
27 com.apple.HIToolbox 0x9357aac9 SendEventToEventTarget + 76
28 com.apple.HIToolbox 0x936eaca0 ToolboxEventDispatcher + 82
29 com.apple.HIToolbox 0x936eadcf RunApplicationEventLoop + 236
30 com.convenienceware.GhostReader 0x000360ba main + 214
31 com.convenienceware.GhostReader 0x00002342 _start + 216
32 com.convenienceware.GhostReader 0x00002269 start + 41
If you need more, let met know. I had to trim it down a bit to post.