I need your help with a decision to use iPhoto. I have been a PC user since the mid 1980's and more recently have used ACDSee to manage my photo images and Photoshop to edit them. I have used ProShow Gold to create slideshows. I am comfortable with my

Question

I need your help with a decision to use iPhoto.  I have been a PC user since the mid 1980’s and more recently have used ACDSee to manage my photo images and Photoshop to edit them.  I have used ProShow Gold to create slideshows.  I am comfortable with my own folder and file naming conventions. I currently have over 23,000 images of which around 60% are scans going back 75 years.  Since I keep a copy of the originals, the storage requirements for over 46,000 images is huge.  180GB plus.
I now have a Macbook Pro and will add an iMac when the new models arrive.  For my photos, I want to stay with Photoshop which also gives me the Bridge.  The only obvious reason to use iPhoto is to take advantage of Faces and the link to iMovie to make slideshows.  What am I missing and is using iPhoto worth the effort?
If I choose to use iPhoto, I am not certain whether I need to load the originals and the edited versions. I suspect that just the latter is sufficient.  If I set PhotoShop as my external editor, I presume that iPhoto will keep track of all changes moving forward.  However, over 23,000 images in iPhoto makes me twitchy and they are appear hidden within iPhoto.  In the past, I have experienced syncing problems with, and database errors in, large databases.  If I break up the images into a number of projects, I loose the value of Faces reaching back over time.
Some guidance and insight would be appreciated.  I have a number of Faces questions which I will save for later. 

Answer 1

Bridge and Photoshop is a common file-based management system. (Not sure why you'd have used ACDSEE as well as Bridge.) In any event, it's on the way out. You won't be using it in 5 years time.
Up to this the lack of processing power on your computer left no choice but to organise this way. But file based organisation is as sensible as organising a Shoe Warehouse based on the colour of the boxes. It's also ultimately data-destructive.
Modern systems are Database driven. Files are managed, Images imported, virtual versions, lossless processing and unlimited editing are the way forward.
For a Photographer Photoshop is overkill. It's an enormously powerful app, a staple of the Graphic Designers' trade. A Photographer uses maybe 15% to 20% of its capability.
Apps like iPhoto, Lightroom, Aperture are the way forward - for photographers. There's the 20% of Photoshop that shooters actually use, coupled with management and lossless processing. Pop over to the Aperture or Lightroom forums (on the Adobe site) and one comment shows up over and over again... "Since I started using Aperture/ Lightroom I hardly ever use Photoshop any more..." and if there is a job that these apps can do, then the (much) cheaper Elements will do it.
The change is not easy though, especially if you have a long-standing and well thought out filing system of your own. The first thing I would strongly advise is that you experiment before making any decisions. So I would create a Library, import 300 or 400 shots and play. You might as well do this in iPhoto to begin with - though if you’re a serious hobbyist or a Pro then you'll find yourself looking further afield pretty soon. iPhoto is good for the family snapper, taking shots at birthdays and sharing them with friends and family.
Next: If you're going to successfully use these apps you need to make a leap: Your files are not your Photos.
The illustration I use is as follows: In my iTunes Library I have a file called 'Let_it_Be_The_Beatles.mp3'. So what is that, exactly? It's not the song. The Beatles never wrote an mp3. They wrote a tune and lyrics. They recorded it and a copy of that recording is stored in the mp3 file. So the file is just a container for the recording. That container is designed in a specific way attuned to the characteristics and requirements of the data. Hence, mp3.
Similarly, that Jpeg is not your photo, it's a container designed to hold that kind of data. iPhoto is all about the data and not about the container. So, regardless of where you choose to store the file, iPhoto will manage the photo, edit the photo, add metadata to the Photo but never touch the file. If you choose to export - unless you specifically choose to export the original - iPhoto will export the Photo into a new container - a new file containing the photo.
When you process an image in iPhoto the file is never touched, instead your decisions are recorded in the database. When you view the image then the Master is presented with these decisions applied to it. That's why it's lossless. You can also have multiple versions and waste no disk space because they are all just listings in the database.
These apps replace the Finder (File Browser) for managing your Photos. They become the Go-To app for anything to do with your photos. They replace Bridge too as they become a front-end for Photoshop.
So, want to use a photo for something - Export it. Choose the format, size and quality you want and there it is. If you're emailing, uploading to websites then these apps have a "good enough for most things" version called the Preview - this will be missing some metadata.
So it's a big change from a file-based to Photo-based management, from editing files to processing Photos and it's worth thinking it through before you decide.