I've been running ie7 on 4 pcs for about 8-10 weeks and the only problems I've had are with norton 2007 crashing it on one machine until norton released a fix early last week.
We have about 20 engineers here, and the majority stick with ie as it does the job and i.t. support it
About half have upgraded to ie7 so far.
if you add the runonce values - make sure they are DWORD !