I use to use NO Xplode. My numbers in the gym jumped up like crazy and I felt like a beast.....up until I felt like I had to shit myself and got headaches all the time. I also experienced some other side effects such as limpdickitis which was really inconvenient (I had just started dating this girl and it was killin my love life).
So I have swore off NO Xplode. I just recently went through my first bottle of Jack3d and it worked great. No side effects, gives great focus, and I can actually feel it helping when I'm at rugby practice and not just working out.
The best pre-workout I've ever used was Biotest Surge Workout Fuel. It's not an NO or pump.It's a whey hydrolysate, BCAA supplement. It really helped me get over a wall I had physically and mentally hit when I started working out and getting ready for rugby. It's really expensive, but worth looking into. You can only buy it online as far as I know. T-Nation has it, but I'm sure you could find it somewhere else as well.