Downtown - worked there for about 2 years, a little over 3 years ago. Still drive through and/or conduct business in the downtown area. Depressing. Kudos to the determined business owners who are not giving up. There was a "business improvement district" initiative started a few years ago. I don't remember the exact name of it, but it's having a hard time taking off; the city either can't or won't spend the needed $$$ to make it a success. I DO NOT feel safe there after dark.
Stockade - Historic. Pretty streets & homes. Residents for the most part take pride in the historic value of their neighborhood. They have home & garden tours several times a year; an art show outside by the Indian. Some great restaurants & cafés.
Vale & Hamilton Hill - Have been eroding slowly over the past decade. There was a time back around 2000-2004 when you could be guaranteed to attend a city hall meeting & see a neighborhood watchdog show up. They would do their best to describe the plight of the area to the city fathers. This was televised on local cable access channel & was really sad to watch. Here are concerned citizens with a solid investment in their neighborhoods & being basically ignored. Vale Cemetery is a prime example. Historically significant; yet filled with vandalism, graffiti, drugs, gang activity, etc. How can anyone pay respects in an environment like that?
Central State Street - Also been on a downhill slide for years. Another place you won't find me after dark.
Union Street & Eastern Ave. - For the most part, both are safe & nice neighborhoods. Beautiful homes; many have been converted into multi-dwelling structures. Parts of the neighborhood are very walkable, esp. Upper Union Street. Nice shops & eateries.
Northside - Don't know too much about this area. Sorry. Some good Italian restaurants though!!!
Bellevue & Mont Pleasant - Some of the streets are starting to get a little tired as more of the houses turn to rentals; but for the most part, IMO, these are nice neighborhoods where family roots run deep. Mostly working class, proud folk. Heavily settled with Italian & Polish families - nice people who aren't afraid of hard work. Great bakeries & such. Some sections getting unsafe the closer to the downtown/State Street drag.
Woodlawn - Some very nice parts of Schenectady can be found in Woodlawn. Again, sketchier as you get closer to downtown...but go back off Consaul Roads & there are some truly sweet areas. Friend of mine is fixing up a little cottage in Woodlawn. Huge yard, safe street, nice neighbors. The house is relatively small, but he won't lose any $ by adding on. Paid less than 65G just 3 years ago.