diff --git a/Cargo.toml b/Cargo.toml
index 86821ee203..3eb9d2959e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,6 +16,7 @@ cookie = "*"
 httparse = "*"
 log = ">= 0.2.0"
 mime = "*"
+num_cpus = "*"
 openssl = "*"
 rustc-serialize = "*"
 time = "*"
diff --git a/benches/client.rs b/benches/client.rs
index f0c27ffbe6..0363a6ce08 100644
--- a/benches/client.rs
+++ b/benches/client.rs
@@ -1,3 +1,4 @@
+#![deny(warnings)]
 #![feature(collections, io, net, test)]
 extern crate hyper;
 
diff --git a/benches/server.rs b/benches/server.rs
index 772cedc7d6..9c71b26bfe 100644
--- a/benches/server.rs
+++ b/benches/server.rs
@@ -1,4 +1,5 @@
-#![feature(io, net, test)]
+#![deny(warnings)]
+#![feature(net, test)]
 extern crate hyper;
 extern crate test;
 
diff --git a/examples/client.rs b/examples/client.rs
index 98b1155980..b2d32667c0 100644
--- a/examples/client.rs
+++ b/examples/client.rs
@@ -4,6 +4,7 @@ extern crate hyper;
 extern crate env_logger;
 
 use std::env;
+use std::io;
 
 use hyper::Client;
 
@@ -20,12 +21,12 @@ fn main() {
 
     let mut client = Client::new();
 
-    let res = match client.get(&*url).send() {
+    let mut res = match client.get(&*url).send() {
         Ok(res) => res,
         Err(err) => panic!("Failed to connect: {:?}", err)
     };
 
     println!("Response: {}", res.status);
     println!("Headers:\n{}", res.headers);
-    //TODO: add copy back when std::stdio impls std::io::Write.
+    io::copy(&mut res, &mut io::stdout()).unwrap();
 }
diff --git a/examples/hello.rs b/examples/hello.rs
index d2bd437a58..4f49bc6266 100644
--- a/examples/hello.rs
+++ b/examples/hello.rs
@@ -1,5 +1,5 @@
 #![deny(warnings)]
-#![feature(io, net)]
+#![feature(net)]
 extern crate hyper;
 extern crate env_logger;
 
diff --git a/examples/server.rs b/examples/server.rs
index f2d806e578..666dc66a33 100644
--- a/examples/server.rs
+++ b/examples/server.rs
@@ -1,5 +1,5 @@
 #![deny(warnings)]
-#![feature(io, net)]
+#![feature(net)]
 extern crate hyper;
 extern crate env_logger;
 
diff --git a/src/lib.rs b/src/lib.rs
index ed937852b7..77f6324558 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,4 @@
-#![feature(core, collections, io, net, os, path,
+#![feature(core, collections, io, net,
            std_misc, box_syntax, unsafe_destructor)]
 #![deny(missing_docs)]
 #![cfg_attr(test, deny(warnings))]
@@ -133,6 +133,7 @@ extern crate openssl;
 extern crate cookie;
 extern crate unicase;
 extern crate httparse;
+extern crate num_cpus;
 
 #[macro_use]
 extern crate log;
diff --git a/src/server/mod.rs b/src/server/mod.rs
index 008af8c41a..3bc4343292 100644
--- a/src/server/mod.rs
+++ b/src/server/mod.rs
@@ -2,10 +2,11 @@
 use std::io::{BufReader, BufWriter};
 use std::marker::PhantomData;
 use std::net::{IpAddr, SocketAddr};
-use std::os;
 use std::path::Path;
 use std::thread::{self, JoinGuard};
 
+use num_cpus;
+
 pub use self::request::Request;
 pub use self::response::Response;
 
@@ -83,7 +84,7 @@ impl<'a, H: Handler + 'static> Server<'a, H, HttpListener> {
 
     /// Binds to a socket and starts handling connections.
     pub fn listen(self, ip: IpAddr, port: u16) -> HttpResult<Listening> {
-        self.listen_threads(ip, port, os::num_cpus() * 5 / 4)
+        self.listen_threads(ip, port, num_cpus::get() * 5 / 4)
     }
 }
 impl<