As C7 points out in his own inane style, the effect of tubes and the effect of tube hype are two very different things. Once upon a time, all condenser mics and all preamps had tubes, because it was the only way they knew how to build them. The recording world did not come to an end. In fact, a bunch of great recordings were made that way, The tradition continued long after the development of the transistor, the FET mic, and the solid state amp.
Good mics and good pres sound better than bad ones, and with very few exceptions, good gear is more expensive than bad gear. If you plug a multi-thousand dollar mic into a multi-thousand dollar preamp, the odds are it will sound good, whether or not tubes are involved. At the current time, good solid state gear is cheaper than good tube based gear, so I usually recommend solid state gear to the budget-concious.
There are tube pres that are clean as hell, and generally they are expensive as hell. Tubes add distortion, which can be subtle, or outright nasty. There are good reasons why most folks don't sing into a Marshall stack. Subtle distortion, we call "warmth" when we like it, and "muddy" when we don't. Clean, we call "transparent" when we like it, and "flat" when we don't.
The attempt to recreate vintage sound has resulted in a bunch of hybrid preamp designs, using a small tube in the front end of the amp to create selective distortion. By and large, they suck, but it allows the markering guru to tell you it's a tube amp. There is nothing I would like better than to own a good tube mic and a good tube pre. That is currently several thousand dollars out of reach right now.-Richie