Pleco Dictionary Users - Feedback

This is a question for anyone who uses the Pleco Dictionary.  I use the Pleco Dictionary for the iPhone, the current dictionaries I've downloaded on Pleco are:  

\"21st Century English-Chinese\"; \"ABC Chinese/English\"; \"ABC English/CHinese\"; \"Adsotrans Chinese-English\"; \"CC-CEDICT Chinese-English\"; \"LDC English-Chinese\".

I'm looking at buying 2 more dictionary add-ons for the pleco, but not sure if they are worth it and would like some feedback.  Does anyone have use with the \"Cheng & Tsui E-C Business Lexicon\" dictionary?  Or the \"Xiandai Hanyu Guifan Cidian\"?  These dictionaries don't come cheap, so I'd like to get other's opinion's first if possible.