Recent observations and theoretical considerations have motivated the study of models for dark energy with equation of state characterized by a parameter w=p/ρ<-1. Such models, however, are usually believed to be inviable due to their instabilities against classical perturbations or potentially catastrophic vacuum decays. In this paper, we show that a simple quintessential model with potential V(ϕ)=Ae^-σϕ and a gravitational coupling of the form (1+|ξ|ϕ^2)R can exhibit, for large sets of

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... conditions, asymptotic de Sitter behavior with w<-1 regimes. Nevertheless, the model is indeed stable at classical and quantum level.