IMO, Mozilla Thunderbird 3.0.4 is rather a downgrade from 2.0.0.24. For instance, TB3 presents commands redundantly when reading an email. This repeating of response-options is particularly noticable on netbooks.

Here are two photos, one from my 11.6" Acer 1410 (64 bit Ubuntu) running TB2, the other from my 9" HP Mini Mi 1000 running TB3. The two photos are presented with identical vertical distance. The redundancy in TB3 and the resulting gobblement of desktop space by TB3 is very apparent, when in the mode of read-an-email.

Click on each image or open in separate tabs to see and compare larger versions.