The 4500 certainly is not a bad choice and still does the job very well (I have one). However, in many areas it is starting to show its age. IMO it is too big, has a too small display, it is slower than many competitors, does not have a very reliable autofocus, its focus confirmation is poor and the battery economy is not very good either - by today's standards. On the other hand the accurate exposure, colour balance, macro capabilities, swivel-body, a true filter thread and many other details make it STILL one of the most versatile digital cameras and also very well suited for digiscoping.
If I were buying a camera just for digiscoping, I probably would take Canon A80 or maybe the new Contax/Kyocera, but if macrophotography is at all important, the CP4500 is still a strong contender.
Ilkka