The problem that I find with Tekkit and public servers is that Tekkit requires a lot more time and resources to get it working correctly and if you play on public servers it's pretty much guaranteed that someone is going to grief so a lot of people rather play on small private servers. In my case I found that some of the mods just didn't fit like Equivalent Exchange which for me ruins the game by making it super easy to produce a lot of resources. Also, playing on a Tekkit server with a lot of players will not be fun in the end because of the massive load it creates on the server so everyone is just going to complain on the lag in the end. I've hosted Tekkit with a couple of friends, we were maybe 12 people playing, and after a while the lag was extremely annoying and that server wasn't ran on someones own computer, this was hosted on a server with 16GB of RAM running Linux dedicated for servers. Our solution was to throw out Tekkit and create our own little mod pack with half the mods that Tekkit have which lead to less server load and a better experience. The only problem with this was that it's a bit trickier to distribute the mod pack without the fancy launcher that Tekkit have. But we solved that problem by simply creating an installer which installed all the files and set it up for the user so they could run it parallel with normal Minecraft.
