One of my favourite places is Le Museum in Montreux (
http://www.museum-montreux.ch/ ) and it's speciality is the steak charbonnarde. As it is set slightly further back, there is no lake view, but the interior is quite traditional with low ceilings and is very atmospheric.
As previously mentioned, La Rouvenaz on Montreux's Grand Rue is also good for Italian food.
Fai Wong Chinese (five mins from the train station) has an excellent selection, although is rather pricey for a Chinese meal, so would only recommend for a treat, but the decor is very ornate and traditional.
If you are keen to get a view, then Le Chalet, opposite Montreux train station, offers a terrace, fireplace and traditional Swiss food.