I did this until very recently. I've used LVM on all my systems since LVM came into being, and did online resizing of LVs as and when required. But after recently acquiring an SSD, the system is on Btrfs, with subvolumes used where I would previously have had LVs. No problems so far, though I'm not yet so trusting that /home and /var are still on ext4 on LVM+mdraid. I might move them over once I have gained more trust in it, though after losing an entire RAID1 Btrfs filesystem after a SATA cable glitch earlier in the year, that won't be for a good while.
For me at least the Btrfs improvements are the immediate snapshotting at the FS level, and that the free space is available to all partitions--I don't have to allocate the space up front to the different subvolumes. It would be great if the distribution installers would automatically use subvolumes appropriately when installing onto Btrfs, though I've not checked recently to see how this improved.