Xcode 4 became extremely slow and kills my hard drive

UPDATE:

The solution was to mock around with #import "header.h" statements. It looks like Xcode requires a lot of processing power for intellisense when you you have complicated / circular imports structure (tracked down by performance tools - Xcode was falling into infinite recursive function call loop). When I moved as many imports I could to the implementation files and used forward declarations in headers, the problem went away.

This is what I have tried before:

1. Reinstalling (complete removal by:sudo/Developer/Library/uninstall-devtools–mode=al) and installed new version4.0.2 - Did NOT help at all. Anyway - Is it really complete removal as my main custom Xcode preference settings has survived)?
2. Defragmentation (iDefrag - full defragmentation with rebuiling B-Tree and Metadata) - Did NOT help at all.
3. System cleaning and antivirus scanning - CleanMyMac, MacKeeper - did NOT help at all.
4. Organizer - Repositories - cleaned all repositories (I use Git and Xcode somehow stores list there for its own reasons even if I use only command line to manage Git) - small improvement.
5. Organizer - Projects - cleaned all Projects from the list except opened ones - small improvement
6. File - Source control - disable Show Remote Status (was enabled somehow, thx to ThomasW for pointing to that), but did NOT help much.
7. Xcode - Preference - General - Disable Auto-Save (prompt only) and both Live Issues (In Editors, In Issue Navigator) - quite a bit of improvement.
8. Closed Utility Panel and Quick Help Pane - the biggest improvement! . I can finally type smoothly again! What a surprise. Such a trivial solution. It looks like help indexing / search assistant simply sucks! Why it does not do lookups in the background or something?

Xcode is still slow but now it is almost possible to work with production quality performance. Anyway it is quite a shame that Core 2 Duo 3,06Ghz / 8BG DDRIII Ram / Momentus XT SS Hybrid can hardly make it. I was so close to buy OCZ Vertex SSD or some other super extra SSD because of this.

I was running into performance problems with Xcode 4 and I tracked it down to the File->Source Control->Show Remote Status feature being on. Turning that feature off did the trick for me.

However, if that is not the issue then you should take samples of Xcode while it is having the performance issues. Either use the command line or the Activity Monitor application. This might give you a clue as to what the issue is. If it doesn't then post the sample here. Also, submit a bug to Apple with the sample.

The following helped me A LOT - purge the workspace file.

Xcode 4 - slow performance

I didn't download the applet they're talking about but just manually doing it is working very effectively so far...

[Update: corrected the link]