Bugs and limitations

Compiling large files takes too much time.
If a known procedure has unused arguments, but is always called without those parameters, then the optimizer repairs the procedure in certain situations and removes the parameter from the lambda-list.
port-position currently works only for input ports.
Leaf routine optimization can theoretically result in code that thrashes, if tight loops perform excessively many mutations. In practice this doesn't happen.
Due to the header representation of block objects, the maximum size of a bytevector-like object (strings, bytevectors, srfi-4 vectors etc) is 2^24 bytes or 16MiB. On 64-bit machines the limit is less relevant, at 2^56 bytes, or 65536 TiB (64 PiB).
Like above, the maximum size of vector-like objects is 2^24 slots on 32 bit machines and 2^56 slots on 64-bit machines.
Bignums are represented by bytevector objects instead of vector-like objects due to the need to treat digits as opaque data. This limits bignums to a maximum value of 2^(2^27) on 32-bit machines and 2^(2^59) on 64-bit machines.