It doesn't fix the problem but it certainly gives a much better indicator on your situation.
If you have 5 bars on iPhone 4.0, it might not be real 5 bars (most probably it might be 3 bars in reality) hence when you do deathgrip it might drop to 1.
However, if you have 5 bars on iPhone 4.0.1, you should only see a drop to 3 bars.
http://fortunebrainstormtech.files.wordpress.com/2010/07/screen-shot-2010-07-15-at-4-57-51-pm.png
Full article: http://www.anandtech.com/show/3821/iphone-4-redux-analyzing-apples-ios-41-signal-fix
As you can see from the chart above, there is significant granularity introduced with the 4.0.1 in terms of showing you the correct bar. Unless you really have SUPERB services, you will probably get 4 bars at the most...
For example, on 4.0, even with -91 db, you still can get 5 bars... with 4.0.1, it will only gives you 3 bars at this signal strength