ToV can be good or bad,depends on your feeling about the first DS
Deathspank: Thongs of virtue is basically the longer version of the original Deathspank with another set of quests, dialogues, locations and inventory items. So first and foremost, it's for people who couldn't get enough of DS. If you got bored through playing it or didn't like the game and you think ToV is going to change anything, you will be disappointed.
ToV's most notable change is switching from medieval settings to modern settings. Some new additions like bazookas, guns ( which are replaced with crossbows ) and missiles on the ground which can be blown up to destroy a large number of enemies are the result of this change of settings.
ToV's story is mainly about getting three thongs of virtue ( out of six ) from three people, a nun, a cook and Santa Clause ( ! ) who are all corrupted by the thong they're wearing. The best thing about DS's story is the fact that it has a great and a somehow thought-provoking conclusion for a humor based game. There are two endings in the game based on a choice you have near the end and both of them are satisfying in their own way.
ToV is two times bigger than orphans of justice. It is certainly a good thing, but DS's game-play with all of its glory, can be quite boring sometimes. So if you try to rush through the game by trying to do every quest and kill everything, you will get tired of the game faster. So it's recommended to play through it slowly, constantly and enjoy your time with it rather than rushing through it.
Also ToV has more focus on solving puzzles and one of them ( searching for the right book in the library ) sounded like an easy version of the similar puzzle in Monkey Island 2.
Visuals, music theme and the overall mechanism of the game-play are all same as Deathspank and changes and improvements shouldn't be expected much in those areas.
So basically, if you liked Deathspank and wished the game was a bit longer, ToV is a no brainer. But if you got bored playing through that short game, ToV probably can't change your mind.