I use Ven-Pie sometimes. The trick is really knowing WHEN to use it. If you use it in the wrong times and France gets the upper-hand, he will be at your back door in no time. The big thing is knowing there's no Juggernaut.
There can be a pile - up on Austria or Turkey, but Italy still needs to know that Russia is his longer-term ally because this buys Italy the time he needs to grab some centers.
I also don't like the opening if England and Germany aren't allied but Italy is expecting to make gains against France. Here it's useless. You have to understand that it may garner nothing. Of it does get you a build, you have to believe you can't keep it long but it's a temporary boost to whatever campaign you're really part of.
It's also REALLY helpful to know that France is moving to Spa in S01. This isn't the end-all-be-all, but it's news you should check into before you move to Pie.
The purpose of moving Ven-Pie is to give France something to stress about. Let's face it, France is a pretty stress-free country, but the moment an army hits Pie in S01, we've got some worries. Is it going to try for Mar? Is it going to hold? Is it really a ploy to get into Tyr? Lots of unknowns bring stress to a country that normally lives a carefree life.
Here's where the real homework comes in. You have to try to figure out what France will do in this situation. The goal isn't to net yourself a build. The true purpose to Ven-Pie is to net France one less build and slow down the west to a crawl. If you believe France is the protective type, then in the fall, you order Pie to hold so France covers Mar and misses out on Spa. The best part is that not only does France not get 2 builds, but also, he can't put his NEW build in as F Mar as retribution.
If you feel France is going to stick it out and call your bluff, move to Mar and take the build. You probably won't keep it, but it's nice to have the second build. You could even opt to produce a fleet in Rom that will pester him further.