diff --git a/src/address.rs b/src/address.rs
index 6b4b334..8eab3f0 100644
--- a/src/address.rs
+++ b/src/address.rs
@@ -28,15 +28,15 @@
 // The idea here is that it doesn't make sense to add two addresses, but it
 // does make sense to add an address and an "address-difference". (If this
 // is too annoying to work with we should let it go.)
-#[deriving(PartialEq, Eq, PartialOrd, Ord, Show)]
+#[deriving(Copy, PartialEq, Eq, PartialOrd, Ord, Show)]
 pub struct AddressDiff(pub i32);
 
-#[deriving(PartialEq, Eq, PartialOrd, Ord, Show)]
+#[deriving(Copy, PartialEq, Eq, PartialOrd, Ord, Show)]
 pub struct Address(pub u16);
 
 impl Add<AddressDiff, Address> for Address {
-    fn add(&self, &AddressDiff(rhs): &AddressDiff) -> Address {
-        let &Address(lhs) = self;
+    fn add(self, AddressDiff(rhs): AddressDiff) -> Address {
+        let Address(lhs) = self;
 
         // TODO akeeton: Do a checked cast.
         Address(((lhs as i32) + rhs) as u16)
@@ -44,8 +44,8 @@ impl Add<AddressDiff, Address> for Address {
 }
 
 impl Add<AddressDiff, AddressDiff> for AddressDiff {
-    fn add(&self, &AddressDiff(rhs): &AddressDiff) -> AddressDiff {
-        let &AddressDiff(lhs) = self;
+    fn add(self, AddressDiff(rhs): AddressDiff) -> AddressDiff {
+        let AddressDiff(lhs) = self;
         AddressDiff(lhs + rhs)
     }
 }
diff --git a/src/instruction.rs b/src/instruction.rs
index d108f5a..8b4b88b 100644
--- a/src/instruction.rs
+++ b/src/instruction.rs
@@ -46,7 +46,7 @@ use machine::Machine;
 //       PC | program counter
 //
 
-#[deriving(Show, PartialEq, Eq)]
+#[deriving(Copy, Show, PartialEq, Eq)]
 pub enum Instruction
       //                                  i/o vars should be listed as follows:
       //                                  NV BDIZC A X Y S PC M
@@ -113,6 +113,7 @@ pub enum Instruction
 , TYA // Transfer Y to Accumulator..... | N. ...Z. A            = Y
 }
 
+#[deriving(Copy)]
 pub enum OpInput {
     UseImplied,
     UseImmediate(u8),
@@ -120,6 +121,7 @@ pub enum OpInput {
     UseAddress(Address),
 }
 
+#[deriving(Copy)]
 pub enum AddressingMode
 //                 length
 { Accumulator      // 1    LSR A        work directly on accumulator
diff --git a/src/lib.rs b/src/lib.rs
index a04965b..1befb1b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -25,13 +25,6 @@
 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 // POSSIBILITY OF SUCH DAMAGE.
 
-// JAM: 'if let' syntax is great for situations where want to match only a
-//      single pattern and ignore all others.
-//
-//     if let Some(x) = foo() { ... }
-//
-#![feature(if_let)]
-
 // Needed for debug! / log! macros
 #![feature(phase)]
 
diff --git a/src/machine.rs b/src/machine.rs
index a9f3e01..27d6184 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -35,6 +35,7 @@ use registers::{ Registers, StackPointer, Status, StatusArgs };
 use registers::{ PS_NEGATIVE, PS_DECIMAL_MODE, PS_OVERFLOW, PS_ZERO, PS_CARRY,
                  PS_DISABLE_INTERRUPTS };
 
+#[deriving(Copy)]
 pub struct Machine {
     pub registers: Registers,
     pub memory:    Memory
diff --git a/src/memory.rs b/src/memory.rs
index 7a489ea..068b338 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -48,6 +48,8 @@ pub const IRQ_INTERRUPT_VECTOR_HI: Address = Address(0xFFFF);
 
 const MEMORY_SIZE: uint = (ADDR_HI_BARE - ADDR_LO_BARE) as uint + 1u;
 
+// FIXME: Should this use indirection for `bytes`?
+#[deriving(Copy)]
 pub struct Memory {
     bytes: [u8, ..MEMORY_SIZE]
 }
diff --git a/src/registers.rs b/src/registers.rs
index 00335c3..3a7c7ac 100644
--- a/src/registers.rs
+++ b/src/registers.rs
@@ -29,6 +29,7 @@ use address::{Address, AddressDiff};
 use memory::{STACK_ADDRESS_LO, STACK_ADDRESS_HI};
 
 // Useful for constructing Status instances
+#[deriving(Copy)]
 pub struct StatusArgs {
     pub negative: bool,
     pub overflow: bool,
@@ -120,7 +121,7 @@ impl Status {
     }
 }
 
-#[deriving(PartialEq, Eq, PartialOrd, Ord, Show)]
+#[deriving(Copy, PartialEq, Eq, PartialOrd, Ord, Show)]
 pub struct StackPointer(pub u8);
 
 impl StackPointer {
@@ -143,7 +144,7 @@ impl StackPointer {
     }
 }
 
-#[deriving(PartialEq, Eq, Show)]
+#[deriving(Copy, PartialEq, Eq, Show)]
 pub struct Registers {
     pub accumulator:     i8,
     pub index_x:         i8,