BTC Guild's primary focus is neutrality when it comes to the network. Unless forced to take a stance (such as the BIP16, version 2 network blocks), the pool follows the standards currently in place in the official bitcoind client. In the event of fast action being required (hardfork earlier this year), the choice will always be the one that keeps the network compatibility as close to 100% as possible with the given options.
When it comes to transactions, BTC Guild makes no prioritization of any transaction, nor does it deprioritize/block any transaction that follows the official client rules. No modifications are made to the selection process, only the block size values (such as increasing the minimum block size to 150kb, and maximum to 500kb currently).
At this time, there are no plans to ever stray from the official bitcoin branch, unless a change within that main branch goes against the above stances, such as blacklisting, whitelisting, or immediate hardforking without a proper upgrade path, long timeline, and REASON to do so that is justified. Example: The v0.8 upgrade which broke compatibility with some 0.7 clients in order to fix the problem of blocks with many affected transactions from being accepted by the network. Once the hardfork was reverted, an upgrade path and time frame were made available in order to move the network forward. The reason for this fork was it brought the client in line with the original protocol, which had a 1MB maximum size, while the 0.7 branch had the chance to reject blocks that fit within the previously defined parameters of what a valid block is.