I exchanged £10s, £20, £50s this summer at Olgas with no problem. I took Euros & a little Sterling with the rest on the cash-passport in Euros - which can be used in the restaurants and shops & can now be used in the new ATM! I havent seen travellers chesques for years?!?
No point worrying about the Euro vs Drachma - what will be will be & it wont change overnight. I think any strike action that would affect the countries income would be unlikely.
Yes the locals have more taxes to pay - the price of petrol has rocketed for one thing but they dont have the problems of Athens the same as a village in Kent doesnt have the same problems as London.