I think its a great engine, especially with DSG. Great economy (circa 70mpg easily on sensible driving on steady runs) pulls well, AdBlue not an issue for me, topped it up once and no issues.
Software, as with all Mk4 Octavia's, is the main issue but if it has 1941 you should be in a good place as its fixed most of the issues.
I agree on the extended warranty, they did a £35 a month deal for me (mine is getting to the 3 year point) for 2 years and also includes two services and MoTs, plus usual breakdown and recovery, so basically £840 for two years, a no brainer for me as I will now be keeping it.