I am in favor of a FAILED impeachment effort: a Congress that refuses to impeach an unpopular president is more likely to be sent packing in forthcoming elections.
If Bush is impeached and removed from office, Cheney (the real controlling force in the White House) will simply step up to assume the role of President. Republicans in Congress will assume they're off the hook, and likely remain in power after the 2006 elections. The American public will go back to sleep, later electing again what they erroneously regard as a conservative president in 2008.
If Bush is impeached but remains in office, Republicans will simply distance themselves from the White House, and again dominate the House and Senate in 2006. The GOP will offer a "real" conservative as a presidential candidate, who might be able to win in 2008.
If the impeachment process is initiated but blocked by the Republican majority, it will be obvious to most Americans that their president and his party refuse to be accountable to them. Democrats will take many incumbent seats occupied by Republicans in 2006, and the GOP will have great difficulty retaining the presidency in 2008.