Just sold my red 87 Civic Si. Still have my neglected project 87 CRX. God I love these cars, and I actually waaaaay prefer the hatch to the crx.
I will say parts are getting way harder to find. 5-10 years ago, you could find stock engines everywhere and they were CHEAP! - to the point where we didn't feel the least bit guilty blowing them up. Now they're drying up. I'm down to a couple blocks and a few "parts" heads, and I'm not giving them away like I used to.
Performance parts are getting harder to find too. Koni stopped making adjustable struts for them a few years ago, and I've seen people asking crack-smoking prices for them. OPM used to sell a mack-daddy adjustable rear bar, but those are long gone. There's a company called Medieval-Pro who started selling torsion bars and some other stuff a few years ago. I hope there's enough demand to keep them in business, and growing.
Civics rust around the rockers. Check the torsion bar mounts and panhard bar for rust. These are not fun fixes, and I'm seeing more and more rust-free cars (certainly by PA standards) that are having panhard bar mounts rust out.
Some people will (especially on redpepper) swear up and down that it does nothing for power, but we've swapped the 1G integra ECU and injectors, advanced the timing as far as she'll go, and seen 93hp at the wheels, which is a noticeable improvement. Also bumps the rev-limiter up 500rpm IIRC.
D16A1 from the 1G integra is a pretty easy swap, though you wouldn't know it by how long mine's taking 
(stalled out because I don't want to paint the damned engine bay, but the rest of the car is too clean not to.) But again, they're also getting hard to find.
Look (ask) for the rear cargo cover, interior sunroof cover/tray, and the BAG for the sunroof. These are usually not in the car, and tough to find. Also, the sunroof screen pictured on the black car is tough to find. Of course, I have all of these things hermetically sealed should you need one 20 years from now. 
PS: If you have a little more coin to spend, Gabe (who used to work for GRM) is trying to sell his 87 right now. Former Hong $200x Challenge car, probably one of the cleanest 3g's in the country. D16A1 swapped, recently passed emissions.
And here's my girl:
