Which VPN Server Hardware is Best for Accessing from Mac Clients
Where I work, we use the Junos line of products for VPN connections.  I'm a little light on the details as far as the hardware requirements and the setup costs etc. but we've had very little issues with them.  Some advantages:


Platform independent

The vpn runs in Java (I believe, I never took the time to look really) and can be run on pretty much any platform.  I've tried on Mac and PC, though if you might need Linux you should check into that first.
Works on iPad


This might be a bit more enterprise-y (read: Expensive) than your company is willing to fork over.  In that case, you might look into the built-in Mac OS X VPN.  Mac OS X Server has advertised VPN hosting capabilities which you can apparently use something like iVPN (though if you're technical with the CLI, you can probably get by without it.)  I don't have any on-the-job experience with this as we're a strictly SOHO environment, but it's for sure worth looking into.

There are enterprise options out there if your company is looking for a managed solution.  If not, there are options for enterprising individuals willing to put forth the necessary time and effort to make sure it all works.  I've experimented in the past with VPN and, though it was years ago and I'm sure the software has matured, I'd definitely prefer a managed solution.