In reply to Sam Maher: Pretty much the only boots I've owned for the last 3 years have been B3 Nepal Extremes.
In October 2009, I had trashed both my climbing boots (Sportiva Trango Ice which fell to bits in short order) and my 4 season walking boots (Scarpa Mantas after 10+ years and two soles) and needed a new pair of boots. I could only afford one pair and since I was going to be Winter climbing in February 2010, I bought the Nepals. Since then, I have never actually got round to buying any B1/B2 boots as I originally thought I would.
The Nepals are a bit heavy but I've never had any great problems even when using them for UK summer hillwalking and scrambling. In fact I was damn glad of them when I was back-packing in the Dales last June in torrential rain - I don't think I'd have dry in anything 'more suitable' for summer backpacking.
Unless you are struggling with fitness or have climbing/walking partners who are all closet fell-runners who want to set speed records for everything they attempt, wearing boots than are 'overkill' for the situation is never much of an issue, provided they fit.