Pls tell me which is the best Photo Manager & why?
I don’t know which one is best but I use Picasa…you can tweak photos easily and upload to your picasa account easily…
I use Picasa… As i find it very simple to use…
Regarding your question, what is your usage type.
I mean are u a Professional Photographer or something having to deal with a lot of Snaps and edit them simultaneously ? or do u want for casual purpose… like checking/shooting family snaps leisurely ?
picasa is gug. Its fast, user friendly and also light on system.
I switched back to ACDSee after using IrfanView for over an year.
IrfanView doesn’t save thumbnails and generates fresh ones every time you open a folder; not fun when you have lots of images.
You need to be clear about what is your expectation out of a photo manager. Based on my requirement I use ACDSee v2.0 which was freeware and light weight. Later versions became kinda fat for my liking and not to mention one has to pay to use.
I have used Picasa for some time. but I preferred ACDSee. I don’t remember the reasons.
iPhoto.. 
I was also using Picasa, but most of the time when i scan the PC for snaps, it takes even those snaps which are of no use or are snaps of the softwares etc.
^^^You can specify the directories to scan in Picasa…simple solution.
Another thing I like about Picasa is the face detection - very useful for me since I forget names quickly.
I was once an ACDSee user but later switched to XnView. It is a freeware, has a rich set of features and supports wide range of file formats
Well it depends on your choice, ACDSee is the first name that comes in my mind, Even Xn-View is good. But i never liked irfan view personally.
If you want a free product, XNView and FastStone Image Viewer are good. You can get them from here:
Regards
Picasa is enough for me.Lightweight and pretty fast.