Setting up a Windoze-friendly VPN

So I'm setting up a system that (among other things) provides VPN access
for remote Windoze clients.

Looks like there are several major packages for this, including
Poptop/pptpd and OpenVPN.  Looks like there's also l2tpd and FreeS/WAN,
but it's not clear how well those work with extant MS clients.  At this
point, sadly, supporting the built-in client is an assumption.

I'm aware that there are some significant differences in how each
package makes security/convenience trade-offs... but given that we're
talking about connecting with MS PPTP I suspect it makes little sense to
get concerned about deep crypto issues. 

Mostly, I'm concerned about reliability, hidden "gotcha" issues and
general robustness.  Stuff like whether going with a product based on
SSL/TLS introduces difficult client cert management issues.

Anyone have any experience using any of these packages in a production
environment and/or make use of some other open source solution I may
have missed?

TIA,

Dylan