I've lived in Lincoln for 20 years until moving to London for uni and I can honestly say it is not a **** hole at all.
Sure it has a couple of rough areas on the outskirts like every city but even that isn't too bad.
The uphill bailgate area of the city is extremely nice with steep hill being named best street in the UK last year. The nightlife isn't like Manchester and London as previously said but its definitely worth going out in. The student nights at the engine shed are good and more and more good live acts have been playing. Zane Lowe does a few student nights in the year which are definitely worth going to and Moda is a really good night that rivals big city events. Calvin Harris and Sub focus have done nights which were insane.
Generally there you notice more students than regular residents so it is what you make it. The university campus is better than most too.
With places like hull, grimsby, scunthorpe, mansfield, boston and gainsborough nearby Lincoln is 5 star luxury compared to those places. Enjoy!