The D100 offers all you could hope for in a 6.1 megapixel SLR. There is a full gamut of control options, aperture priority, shutter priority, manual etc. I tend to use aperture priority for flower pictures, and use a high or low aperture setting depending on the type of image I'm looking for. ISO settings are 200 - effectively 3200. The camera tends to under expose and therefore I usually have it set to +0.7 or even +1 overexposue - I can't understand this, presumably something to do with the camera's algorithm settings - but it is common to this camera.
Currently I do not use flash, but there have been times when it would have been useful. I have used a set up in the past of two Nikon SB 17 guns on a home made bracket, which gave me TTL flash with my old 801s cameras. I was about to buy the Nikon SB29s macro flash recently, only to find out at the last minute (in spite of this not being made clear in the Nikon D100 brochure!) that it does NOT give TTL with a digital camera!! I cancelled my order, and found out that Sigma have just released the EM-140DG macro ring flash, tailor made for digital photography - retail expected to be about £300. I'll wait and see.
There is a problem (which you don't get told about by the retailers before you buy the camera!) of dust on the CCD in the camera, when you change lenses (and what's the point of buying an SLR if you're NOT going to change lenses?). This can creep up on you quite quickly - and you only become aware of it when you return home from a day's shooting to view your results on screen, only to find black dots over the image which realistically cannot be removed. There are two options to clean the CCD - 1. return it to Nikon - cost £200+ (quote from Jessops) - this will get very expensive if each time it gets dirty you do this, not to mention the fact that the camera will be at the 'cleaners' more often than you have it in the field! 2. clean it yourself - I chose this option and have, so far, had no problems. However, you do need to buy a Nikon EH-5 (£100+) to keep your shutter locked open while you do the cleaning. There are good web sites available which explain how to clean it safely, and then, finally, you also need to buy the cleaning materials!!!! (Wouldn't it have been nice if all this is made clear to you BEFORE buying the camera!)
I also have had a SERIOUS problem with damp getting into the body - it is currently at Nikon for repair - the estimate is £434. I have used 4 Nikon film SLRs in the past for over 15 years and never had a prolem with this. Nikon say that digital SLRs are more vulnerable to damp than film SLRs - thanks! But I still fail to see how a camera body costing £1000 should not be better able to deal with the British climate! A salutory lesson for all. (Grizzle over!)
The Nikon Coolpix 4500 is an excellent camera to have in your pocket - fairly portable, 4 Megapixel. I tend to shoot in macro mode for flowers. It has aperture priority, shutter priority, programme mode and manual. Focusing is a little tricky outdoors, when trying to view the LCD monitor. There is a manual focus of sorts, but I prefer to use autofocus. ISO range is a little limited (200 - 800). I originally bought it for use on a telescope, since it still is probably the best camera for Digiscoping of birds. It is an unconventional style with a rotating half of camera, which does have its uses. Start up time and time delay on pressing the shutter are a nuisance, but more of a problem when photographing birds than flowers. It may be deleted from Nikon's armoury soon. Price - lowest I've seen recently about £350.