This is one of my top favourite shows. As with most of them, it is a bit dated, especially the first season, and cheesy, for sure. But the writing, the wit and charm of the show, doesn't get old. Yes, there are some bad episodes, annoying characters (Dawn), etc. But there are also some awesome episodes (like the musical, and "Tabula Rasa", that followed it), and when the show moved to the CW, it came back a bit darker, more grown-up, than it had been, and yes, while there were (again), some bad episodes, the show needed to grow up a bit. That's where "Angel" did well, and Buffy got to the same place when it got picked up by the CW.
I love watching this show over and over. I think seasons 3 and 4 are my favourite over all of them. I love Spike, how he grows and changes over the seasons, and the show had a good ending to it, I am glad it was allowed that. (If it had ended in season 5, as originally planned, it felt a bit unfinished, but that was a good season finale as well).