End of May 2009, the program of all the free concerts and events of the Montreux jazz Festival 2009 was released. 
Even if you do not attend any of the major concerts, I believe it really worse doing a tour in Montreux as the atmosphere is really special during this period. 
Of course if you do not like the crowd, avoid week-ends. 

Since 3 years the hotel Royal Plaz Montreux did a strong partneship with the jazz and now offers in their conference centre (it is too noisy to make a conference during this period...) a very trendy place for house lovers called the Studio 41. 2-3 dj's per night like Sir Colin, Mr Mike, Miles Numan, or Igor Blaska will make you dance from 11pm until 04-05 am. 
 
This venue is really packed every day so avoid to come in between 00h00 and 02h00 as you might wait for 1 hour before to enter. 
The great thing about the Studio 41 is that it is surrounded by a garden and there is also a nice terrace to enjoy the evening without too much noise.