It worked for me yesterday.
worked fine even today and just try to restore another iphone and failed so i followed this instruction to get my iphone 4 up & running ...
How to Downgrade from iOS 4.0.2 to 4.0.1
Step 1: Lets download your SHSH blobs from Sauriks server to your computer. To do so, download TinyUmbrella and plug your iPhone in. Select the Advanced Options box. Also select the firmware version to which you wish to downgrade. Finally, select Cydia under Request From. Then hit Save My SHSH. This will grab your SHSH files from Sauriks servers and save them on your computer.
Step 2: Download the firmware to which you wish to downgrade to from our iPhone downloads section. Save it to your desktop.
Step 3: Put your iPhone in DFU Mode. To do so, launch iTunes and plug your iPhone in. Press and hold the Home and Power button together for 10 seconds. After 10 seconds, release the Power button while still holding the Home button until iTunes pops up and says it has found an iPhone in recovery Mode.
Step 4: Run TinyUmbrellaand click the Display SHSHs button to make sure your SHSH blobs were downloaded to your computer. Once done, click Start TSS Server.
Step 5: Now were going to restore to the firmware you want. To do so, launch iTunes and plug your iPhone in. Hold to SHIFT key (Windows only) or ALT/Option key (Mac only) while clicking on Restore. Make sure you hold the key while clicking Restore. A window will open. Simply select the firmware you downloaded in step 2.
Step 6: Your iPhone will start the restore process. You will most likely get several errors (error 1011, 1013, and 1015) but thats ok, dont worry about those.
Step 7: Finally, we need to get your iPhone out of recovery mode. To do so, simply click Kick Device Out of Recovery in TinyUmbrella.
Done!
You should now be back on a previous iOS, giving you the ability to jailbreak and unlock.