Getwork - can the miner increment timestamp? When requesting getwork from bitcoind or a pool, the miner is expected to be incrementing the nonce value of the block, but can it also increment the timestamp value, or would such tempering cause a submitted work to be rejected by bitcoind or a given pool?
Yes, the miner can increment the time stamp by a limited amount, but only if the pool advertises X-Roll-NTime as a feature. DiabloMiner and CGMiner both support this.

See the official spec for more information.