The 505 is/was indeed excellent. I'm from the UK, I imported one fairly close to the US launch for £175. Money very well spent, it served me well till I foolishly sold it because I thought the iPad(1) would replace it as my main reader. Wrong. iPad has its strengths but I'm no fan of it strictly as an ereader - too unwieldy and glarey imo.
So, I relented and bought a 650 and have no desire to upgrade from that any time soon. Had I not sold the 505 I'd still be happy with it probably. I was fortunate when I sold it, as the x50 models were yet to even be announced and the 505, then discontinued, was perceived as better than the 600 so the price had held - sold it for £174, £1 less than what I bought it for 18+ months earlier