I have Thomastik Infeld Jazz Rounds on my F-Bass BN5, Jazz Flats on my Godin SD-4, and Spirocores on my upright.
I'm still adjusting to the Rounds-I like their loose feel and broken-in new sound but I'm wondering if they'll have enough edge when they're a couple months old. I'm also not entirely thrilled by the low B which sounds a bit indistinct and hollow compared to the other strings. Plus it took Juststrings.com about 2 months to get their shipment from Austria. Like Jeb I find that most light/medium nickel rounds (particularly D'addario and Dean Markley) give me what I want for a lot less money.
OTOH, I'm thrilled with the Jazz Flats-they feel and sound amazing--Old-school fat,warm and punchy--but no mud. They turned a good-sounding bass into a great-sounding one. They're particularly good when played with a plectrum, and loose enough for slapping and tapping. That inner silk winding really does something for the tone and feel. Very classy.
The Spirocores are THE classic jazz upright string, known for their ability to be both warm and cutting when played pizzicato. Played with a bow these strings tend to sound pretty gravelly, but this can help project the sound. All in all, I'm impressed by TI's strings.