Well, forgive me for extending the thread into details many perhaps do not need BUT,
could be a little misleading to some. Assurances that you're talking to your server? No different client behavior between a personal/private cert and a commercial cert here. At least after the first time you've accepted that personal cert. If the IP changes, you'll be warned.
As for further use cases -- beyond providing encryption for any data you might upload to a particular service(calendar, intranet, finance mgmt, etc...)?? Since I'm guessing you know better(as a regular contributor to DH forums and it seems to me a somewhat savvy IT user), forgive me if I sound pedantic as I get on a pedestal...
Never trust your network. Sure if you're at home and you're confident your control over that network is "perfect" or you don't care if some sniffer/snooper can see your date plans for the weekend, that's one thing. But you might want to get into the habit of treating even those bits securely so you don't have to think about it when out on a network you don't control(like the coffeehouse, school, work, etc..). Especially if you've setup personal intranets or other services that may contain sensitive information. Though I've already alluded to the fact that in the end, you are putting your trust in the guys and gals of DH(even if you're paranoid enough to encrypt your data repositories).
Coming back to the issue of purchasing a personal vs commercial cert, it is again important to understand the real purpose behind a commercial cert. It[commercial] does not increase line/IP security per se but serves to vouch that you are who you say you are. Even at a cheap $19.95/yr, I have no need for such a service for myself or those who personally know me. The same goes for internal small biz services. Not necessary. Remember, you can accept the personal cert and not be bothered by pop-ups unless something on the line changes(web server, IP).
I don't doubt this has been an incomplete discussion of the issues around HTTPS certs here, so for those interested in more info, I encourage you seek out additional info.