Someone asked whether I had any experience with SBS and using a dynamic DNS provider (such as TZO or dyndns). The answer is yes and yes.
At home, I used TZO for about a year before finally getting a static IP address. I had no problems with TZO, their setup was awesome and worked with practically no problems. For a Standard SBS server your experience should be the same. For my case, I was using Premium and ISA, and it required a bit more work (of course).
First, why was I using ISA? Not because I really needed it. Unfortunately, the phone company in Seattle that is known as Qwest has quite possibly the worst DSL setup known. But to get my DSL, I had a USB port modem that required me to "dial" a connection to get established. Since it was a USB modem and not a traditional modem, RRAS wouldn't recognize it as a dial-up adapter and therefore wouldn't do dial-on-demand, so I had to use ISA to establish the connection for me. I couldn't use CEICW for some weird reason either (even though I designed it :-), so I had to this all by hand, which made me recognize once again how good a thing the CEICW is.
Anyway, I got that all up and running, and the TZO part was a snap. I even needed to create a custom A record and that was no problem either. If cost wasn't an issue, I'd recommend TZO in a heartbeat, but my understanding is that they're actually pretty pricey (I haven't compared recently, so be sure to check). I eventually stopped needing it when I switched ISPs and finally got a decent DSL modem with a static IP. (I can go into that nightmare in a different post)
In our testing environment here at MSFT I know we've often used DynDNS, and that also seems to work with no problems.
So in short, go ahead and use dynamic DNS providers, they should run with no problems. Make sure the provider can run as a service (and not as an application) so you don't have to login to make sure your records are updated.