I see a lot of people using pre-workout boosters and I tend to question myself if they are really necessary for the average gym user. I can understand it for pros though as they potentially have more frequent training. While using them you are actually tricking yourself to feel better. Wouldn't it be better to just listen to your body and react accordingly?
I think the first question that needs to be answered is "do workout supplements have any effect other than placebo?". The answer to that depends on the supplement and what you consider to be a reasonable effect. Creatine is a classic example of a supplement that has a proven effect with relatively few side effects. If you're pushing your limits, creatine can push you a little bit further. Protein supplementation works in a fairly obvious manner — if you don't have sufficient protein in your diet, your body can't manufacture muscles — but most casual (non-vegan) lifters are probably already getting enough protein.
As for commercial products, they run the gamut. Many of them are just protein powder or creatine, sometimes with a B.S. ingredient added so that they have a "proprietary blend". More dangerously, some of them are essentially prescription pills, whether they've isolated a particular chemical compound and added it in (Jack3d's purported signature ingredient is ostensibly extracted from geraniums although it's been proven that they'd have to process several tons of geraniums for each bottle, so it's more likely they're just dumping the chemical in) or, in some cases, they're actually grinding up pills and adding them to the mix. Supplementation is a very unregulated industry, and the companies involved pay good money to lobbyists to keep it that way.
Of course, there are also non-supplement options. Taking a painkiller or anti-inflammatory such as aspirin can let you lift longer because you don't feel the pain as much. Caffeine can boost your performance. Glucose will keep you moving. Notably, many of these chemicals are added to your typical supplement mix and then sold at a substantial markup. In the end, other than protein and creatine, that's how most supplements provide the effect that they do.