Sage ACCPAC CRM.....Stay Away!
We use Sage CRM here and though it is customizable to work with GTD (sort of) I find myself migrating back to simply using Outlook to manage tasks and projects and use CRM only as a Database and simple marketing tool.
With Sage you can intergrate with Outlook, but it is rather cumbersome to do so. To file an email against a customer's file is at least a 2 or 3 step process, which is completely counterintuitive to the GTD mentality (and is way too easy to simply not do).
On top of that, you can use SAGE CRM to send email, but not receive them.
And who wants that? It's like having a car that turns right but not left!
I have friends who are in the business of being computer nerds and they swear by Microsoft CRM only! (perhaps because they're MS Platinum dealers?).
I have played with Microsoft CRM a little bit, and it seems to be a great product.
Salesforce.com as a GTD Solution
There is a great interview (one of my personal favorites) with Ismael Ghalimi in the Connect Library (you can find it here: https://secure.davidco.com/connect/m...29&trackid=479) where he talks about using Salesforce.com as his GTD system. I talked to Ismael at the GTD Summit as I am using Salesforce.com daily to get a better idea how he implemented it and he pointed me to his very interesting web site (http://itredux.com/extreme-productivity-seminar/) where you can find some more information on his approach.
I didn't go down this path for a number of reasons (mainly I am not allowed to implement the customizations in my company that would be required) so I am still using OmniFocus on my Mac and iPhone which works great for me.