I have to agree with Bean, who is slightly against them, but I am most certainly for the use of them as a one time beginning game purchase.
As the game ramps up and levels are accumulated, the potions will certainly prove to be more of a waste of money as it will be taking you away from getting closer to the items you need to actually cause the enemy team some issues.
That said, however, I believe they would be very important on the opening face off. As people have said, the average of 50% life regen from them increases your time farming, which will pay off the potions and bring in profits to get the items you will start building. Survivability is also a factor: if you and the enemy have beaten each other to a pulp, and the enemy goes back to get health, you can pop a pot or two to regain health there while continuing to farm; you might even get a few first swings at the almighty turrets.
While the enemy was at base, what did he get? Nothing. No farm, he has to run back, and you have a mild advantage being ahead on the turret attacks. Only mild, but something is better than nothing!
The game is situational. Sometimes, a potion will be useless and wasteful early game. In a situation where, like Bean said, you're taking risks and possibly getting killed because of them, pots would be useless and wasteful... but if used correctly, they're amazing.
Basically, if you do it right, you do it right. If it helps you play better, last longer, and notice a benefit early on, then go for it.