Yes, indeed, the unreliable and changeable weather is the only tourist trap I can think of.
I will not mention some high end restaurant that could have been a trap if I went there.
I mean "Masons" restaurant on the second floor of "Kryivka" restaurant at 14 Market Square and some other upmaket places.
Forewarned is forearmed.
There are many more simple cafes and restraunts to explore, not necessarily those VIP places...
Unique Suggestions: find out about the price range of cafes and restaurants before choosing one.
Fun Alternatives: Do your Internet search before deciding where to go.
VT is a great help here!
Have fun, fellow travelers!
I really can't say I have been sucked but there is one warning I would like to address. As in my home country, in Ukraine the 1st of May is celebrated. So make sure, if you want to visit around that date book a lot in advance. And make really sure that your hotel has your booking. I have been tricked by Hotel Eney about my reservation and in the end I had to look and 10 o'clock in the evening for a room in Lviv around 1st of May. I was able to find only one room for one night at Leopolis hotel at the price of 170 Euros/night (not that it was not worth it:)
Fun Alternatives: There is no alternative, book in advance, confirm your booking and pray that everything will be ok!
I haven't found anything in Lviv that I could call tourist trap. There are not many things you have to pay and what you pay is usually a good value for money. Although Lviv's center is listed under UNESCO world heritage list, tourism is still in infant phase. There are some tourists coming, mostly Poles and Slovaks (I have also seen Croatians, Africans, few Germans and Italians...) but the city is still pretty genuine.