Lets just say the 380SE gathers speed in a dignified manner.
Its not fast, but it has no problem keeping up with traffic.
If you have AC/heat register problems, a likely cause might be one, or several, of the vacuum change-over valves which are located to the right of the radio. They are powered all the time so its not surprising that a couple would fail. If the heat fluctuates widely, a likely culprit is the air sampler fan to the right of the glovebox. That too is powered all the time.
Stumbling idle is fairly common. If you are handy, invest in a multimeter with a duty-cycle reading to check on the O2 sensor and idle mixture. Also a CIS fuel pressure tester will pay for itself in one use, to test system and control pressures. There are lots of little tricks to avoid spending big bucks. This is a DIY vehicle for the most part. Lots of good info in the mercedesshop archives too.
Good luck with your car. Mines a daily driver and its great.