  Based on the full BaBar data sample of 466.5 million BBbar pairs, we present
measurements of the electron spectrum from semileptonic B meson decays. We fit
the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM)
suppressed B -> Xu e nu decays from the CKM-favored B -> Xc e nu decays, and
from various other backgrounds, and determine the total semileptonic branching
fraction BR(B -> X e nu) = (10.34 +- 0.04_stat +- 0.26_syst)%, averaged over
B+- and B0 mesons. We determine the spectrum and branching fraction for
charmless B -> Xu e nu decays and extract the CKM element |Vub|, by relying on
four different QCD calculations based on the heavy quark expansion. While
experimentally, the electron momentum region above 2.1GeV/c is favored, because
the background is relatively low, the uncertainties for the theoretical
predictions are largest in the region near the kinematic endpoint. Detailed
studies to assess the impact of these four predictions on the measurements of
the electron spectrum, the branching fraction, and the extraction of the CKM
matrix element |Vub| are presented, with the lower limit on the electron
momentum varied from 0.8GeV/c to the kinematic endpoint. We determine |Vub|
using each of these different calculations and find, |Vub| = (3.794 +-
0.107_exp +0.292-0.219_SF +0.078-0.068_theory)*10^{-3} (De Fazio and Neubert),
(4.563 +- 0.126_exp +0.230-0.208_SF +0.162-0.163_theory)*10^{-3} (Bosh, Lange,
Neubert, and Paz), (3.959 +- 0.104_exp +0.164-0.154_SF
+0.042-0.079_theory)*10^{-3} (Gambino, Giordano, Ossola, and Uraltsev), (3.848
+- 0.108_exp +0.084-0.070_theory)*10^{-3} (dressed gluon exponentiation), where
the stated uncertainties refer to the experimental uncertainties of the partial
branching fraction measurement, the shape function parameters, and the
theoretical calculations.
