Interiors, not my most favorit job, but for my website, I have to do a lot of it.
Taking pictures in interiors, I always hated the lightfall away from the windows, making it darker along the walls. And, in trying to get a balanced lighting, its difficult including the windows, they are mostly overexposed.
I started out with available lighting, using those cheap construction lights in 300 and 500 Watts. They tend to get hot and the lighting wasn't really controlable with outside colortemperature, so I didn't go on with it.
Later I used to carry around a large studio bag, with two old Metz 60 ct 4, my dynax 7D and two 56 or 54 flashes. Because of the flashes, WB on daylight. I use one flash on the 7D as trigger, all are manual set, triggered with remote eye.
Like David I tried those cheap China things, but not reliable at all.
Setting all flashes manual means you rely heavily on the display to judge the image, and how to increase or decrease the flashes. All flashes have an extra diffusor from Omni bounce, cause I take pictures with wide angle. Until the a900, that wat the KM 7D with a Sigma 15mm fisheye. PTlens als plugin for PS is then used to correct the image. Now I'm trying the a900 with Sigma 14mm. I still need some practice getting decent results with the a900.
Using the flashes in interiors, I learned the following: Light from the flash on the camera, makes it difficult for even lighting. Lightfall away from the camera doesnt make nice pictures. So the flash on the camera is used more as a fill.
Flashes placed higher or lower, make shadows on the walls, if lighting is a bit balanced, you can minimize it but not eliminate.
If possible, I setup flashes in the direction of the walls to be lit, but nut always. I recently found that in order to get even lighting on walls or ceiling ( with those wide angle lenses... ), flashes can be in some position where they bounce against walls or ceiling, but visible in the picture too. Or shielded by some furniture. Lighting is then actually in the direction of the camera. Gives an unreal effect, but not unwanted as I see it.
More recently, I bought an 800 Ws studio flash, to get light indoors, wile still being able to get good exposure for the outside view. I'm now experimenting with pictures taken outside, in the direction of the house to show something like the balcony, and at the same time also some interior. flashes indoors must be fired too, hence the remote control tests. Looks like David is right on that subject......
At the same time I'm a bit experimenting with HDR but I don't find to much use for it, nevertheless I'm sometimes trying it to see if I get decent results.
Most of the time I find it hard to get decent results, sometimes it works, and some days nothing works. Results of a decade interior pics can be seen at my website
http://www.cadzandbad.info A good observer will recognize the days of tungsten light and poor scanning of film. This summer I've taken may pics new, and the 2009 season again I'm planning on doing most images again. So I welcome all advise and critics......