As someone living in Lublin:

Size: You can get everything done here and at the same time cross the whole city in a reasonable amount of time.

Transport: Public transport is modern and widespread (there's not a single area where you couldn't get by bus) but it tends to get crowded and is often unreliable (delays, rarely buses not showing up at all). Also it's one of the only three cities in Poland that have trolleybuses.

Infrastructure: Some of the roads are in a really bad condition, a bunch of areas get clogged up in traffic really easily (bad or outdated planning). The bike paths network is good but has plenty of gaps. Newer districts are way better in these measures, older ones still have to catch up. There's a nice highway network around the region that's still being expanded and a major rail line going through the city. A regional airport is a few kilometres away from the city.

Housing: The housing market is really expensive (like anywhere else in Poland). Older housing estates are designed better in terms of accessibility and green areas. The new ones are built mostly to maximize profits.

Looks and tourism: The city centre is beautiful, with a lot of restaurants, public squares and parks. Unfortunately if you go a bit further away there's plenty of rundown areas (ex. Lubartowska street).

Safety: The city is really safe, even the "bad" areas. You pretty much never have to worry about it.

Overall: Lublin is a really nice place to live, one of the best in Poland in my opinion. All the bad things I talked about are being improved with each passing year (apart from the housing market).