The general wisdom I've seen here is that no handheld has as good a preamp as what you can get from an external unit, nor are the A/D sections as good as those in a V3 or a big all-in-one like a DR-680 or 722. That being said, I haven't been displeased by the LS-10 line-in, and the LS-11 should be similar.
The LS-11 also gets rid of the mic-in bass rolloff that affects the LS-10. Nevertheless, my ears > SP-TFB-2 > LS-10 configuration has given me very nice results without resorting to EQ.
It's worth keeping for low-profile and quickie grab-and-go situations. At some point I want to get a Littlebox, though; using my E-MU 0404 USB as an "analog" preamp adds an extra A->D->A conversion to the chain, not to mention that it needs an external power source and the 0404 is definitely not stealthable.