I'm new to flatwounds, too. Just having bought a sweet semi-acoustic bass, Yamaha BEX4, I decided to try some flats on it. I ran through the stores and found a set of D'Addario Chromes. Put 'em on 2 weeks ago, and here's my experience. I did encounter some problems with the left hand fingering, my fingers tending to slip a bit along the string. For the first time it was a big inconvenience for me. But each time I took up my Bex again, I felt more and more comfortable. I found myself adapting very quickly, and the third try was much more pleasant than the first one, even though right now I'm spending most of my playing time on a five-string fretless axe with nickel rounds because I'm curently gigging with it and rehearsing for these gigs, so I just do not have much time to play anything else. I do not play flats every day, but nevertheless they become easier to play each time I try'em.
But the other surprise with the Chromes I found that they are just too damn bright! I had never thought that I'd get more finger buzz and all the nasty metallic zing from a set of flats than from any roundwounds I'd ever played, no matter nickels or steels! That's what I really dislike. It is clearly heard when playing unplugged, so this is the real acoustic output of the strings themselves, and nothing else. I have to cut the trebles and high mids on my amp more than with the other basses, though while still with the stock roundwounds that had not been the issue. Soloing the neck pickup removes most of the zing (though not completely), but when I try to add in some piezo, the result is not so sweet as it has been with the stock rounds, just because all the zing and buzz, that's clearly heard unplugged, gets amplified. That's not to say I don't like the tone - in fact, I do, though for the first couple of times I had some nostalgia for the sound of the stock rounds (completely different from the flats, of course!), but the more I played, the more I liked the new sound - very clear and even throughout the frequency range, not unlike the Steve Swallow tone. If just not the zing....... Maybe in another couple of weeks of playing, when the strings get older, it goes away. More accurate playing should also help, I guess =) Or maybe I should try a flat set from another vendor, don't know. Though I have to admit that playing against a record (haven't had a chance to play my Bex in a band yet) was a really nice experience - all the zing just sank in the hi-mid wall of sound from the other instruments, while the low end was there, present and well articulated. Still, I'm in doubt... Any suggestions would be appreciated!