I used them for about a year and a half. Most of what I play is arco- probably about 90%. Even the non-classical stuff I do usually has some arco in it. For me, the 180s were the best sounding strings for pizz that I've ever played. They were also very good arco. But not quite good enough to stop me searching for something better...
I have the Bel Cantos on right now, which are better (different) for arco and not as good for pizz. Awaiting Evah Pirazzi...
The Compas 180s feel really good under my left hand. They're a bit thicker than regular steel strings and I preferred that, even though my hands are fairly small. I like the sound also, and feedback on chamber orchestra gigs was positive. For me I just didn't like the feel of them under the bow well enough. I'm not sure how to describe it, but something like 'not contacty enough'. I've given the set to a student though, and his bass sounded better immediately.
They are very finicky strings, and a pain to install, especially the long E/C/B. They are brittle and will break if the wound part gets onto the peg at all. Two broke on me (a long E and an A), so reliability was an issue too- it wasn't a lot of fun having to play two morning concerts with no A (a good challenge though but the kind of thing you really shouldn't have to worry about!). There's a thread here somewhere about Velvets breaking.
Don't know if that's of any help, but there you go.