[jyl]

This is something you really should have figured out before you bought.

Well, what's done is done.

I've looked at the issue, because my neighborhood periodically thinks about whether to apply for the designation.

The consequences vary and you really have to investigate the restrictions and benefits in your particular case. But in general:
- Some restrictions on exterior modifications to your house, which may or may not be onerous.
- Sometime there are tax benefits.
- Some protection from development, e.g. no apartment buildings or big commercial devs going up in your neighborhood

In general, I wouldn't be fussed about it, unless you were planning to make some fairly significant additions and/or have very individualistic tastes in color, style, etc. When the issue next comes up for a vote in my neighborhood, I will probably vote "for" the designation.