A good dictionary 'to go' seems appealing. Anyone who relies on a high quality and timely content knows the 'Oxford Dictionary of English'.
With over

• 355,000 words, phrases and definitions (including 3,000 new)
• example usage
• word origins + encyclopedic entries

When you start the application for the first time, the dictionary will be downloaded (MSDict format) to the phone memory or your SD card. Subsequently, everything is also available offline.
What makes this dictionary especially useful:

• Search results are displayed while you type
• Hyperlinks are shown on the results pages and 
• The history of recently looked up words can be scrolled through

Both content and the technical implementation (by MobiSystems) are done pretty well. But unfortunately, due to the  application's high price, we can not assign the highest rating here. 'Oxford Dictionary of English' costs € 29,99, which is only slightly cheaper than the dictionary's hard copy (more than 2000 pages for € 31,95).