Temporary Image Retention or temporary embossing of content on the screen still exists in Plasmas of some of the vendors. But it has been reduced to a large extent.
LED- Great resolution. 1080P Full HD. Response times/Refresh times are decent, Much better blacks than LCD. But being sold at premium as it is the newest technology on the scene. Also any major cons or issues with LED are yet to be known.
LCD - Great resolution. 1080P Full HD. Response times/Refresh times is improved in newer models - please check if the model you are looking at has a good refresh rate, Blacks are not that great on LCD, colors are a bit artificial. Backlit technology so both LCD and LED works good in brightly lit rooms. SD content does not look that great (some sets have good image upscalers built in)
Plasma - Excellent SD pic quality, decent HD image view, Value for Money - you get the biggest screen in amount spent (for HD ready sets), Good Blacks (not from LG - check Pana and Samsung for the same), Real colors, Excellent refresh rate. You need to be careful for TIR and prevent any burn in.
Whatever you buy will suggest staying away from 32 inchers.
Happy Buying Brother!