It's kind of like what I said earlier in this thread: if you want true tube coloration you need to go with real tubes. The plugin is giving you an *effect*, not actual tube coloration. The tone of real tubes can indeed be very subtle.
Your ears may need to get used to the sound of good tube gear. It's not what you might think it is. I do find the "effect" to be subtle, but the overall tone to be a bit rounder and more pleasing to the ear. It's more about tone than effect, and this is where some go wrong. You read a lot of posts on message boards where people want to use tube gear as an effect, and often those same people are a bit dissapointed when they actually use real tube gear. Also, the better the gear, the more clean and subtle the tube sound will be, as far as the "effect" of it. The tone will be nice though.
But again, the plugin is giving you a drastic effect, not the true sound of good tube gear.