I have not used them, as there is a decent lab near me. That said, I know several photographers who use mail order service to have their slide film developed and have had great sucess.
To put it delicately, these people are smoking the minty fresh crack. The Kodak Gold series has the worst color I have ever seen for a modern print film.
Quite the opposite is true. Velvia 50 (and its two cousins, 100 and 100F) are quite a cool film, and tuned for daylight. Skin tones are quite pale with it. It is true, V50 is not the best for portrait photography unless one is looking for a specific artistic look or is really good with the use of warming filters. I have not shot many other slide films besides V50. I have made use of Fuji's Sensia line (particularly the ISO 200 iteration) and liked it.
As for price, it's all relative. A 36 roll of Velvia 50 is $12-13 around here. Superia is even more expensive ($15+). Processing fees for slide film is more expensive than print film as well. Kodak does make some decent color print films, like the Ultra Color 100UC, but they're at least $10 for 36 exposures. The moral here is that film is expensive. 35mm is still a bargain compared to what medium and large format photographers must cough up. My friend Eddy pays $2 per frame for Tri-X in 4x5" sheets. His friend shoots 8x10" and pays $4-5 per frame for the cheapest film he can buy. He said Velvia (the now-discontinued original, not the new Velvia 50) was $18 for one 8x10" sheet, and twice that to have it developed.
The advantages of film is that the bodies are cheap on the used market, don't get obsolete, and of course when it comes out right, film beats digital hands down for image quality.
Lastly, one of the great joys of slide film is cross processing it. As it turns out, Fuji slide film stock is very hearty and holds up well to rigors of cross processing. This is especially true for Velvia 50.