I primarily bought the Vector as a rugged watch for when I'm trekking, which could also be used as a backup compass. I soon found that the altimeter proved to be an excellent navigation aid when combined with the ability to take bearings quite easily with the watch in compass mode. The barometer is good too as it indicates change in air pressure so you get an early indication of changes in the weather although of course if you are going up/down mountains, the usefulness of this becomes limited.
It's weathered well (I've had it over 10 years now), although there is a large scratch on the glass, picked up while walking in the Pyrennees. This hasn't affected performance at all though.
My only negative comment is that although you are advised in the manual to recalibrate the compass before every trip, the process can be a bit time consuming so it doesn't get done as often as perhaps it should. This did on one occasion cause some confusion since I used the Vector to make a quick check on the direction I was taking and it turned out to be wildly off. Fortunately I was aware of the general direction I needed to go so got out my 'real' compass to check, which is how I found that the calibration had gone completely. As I say, recalibration can be a pain so it's not something you feel like doing at the beginning of every day.
I also tend to reset the altimeter when I get to a known height, usually a peak, since changes in air pressure due to the weather rather than altitude can make the readings slightly inaccurate over a period of a few hours. Resetting the height is a job of a couple of seconds so this isn't an onerous task.
When it comes to battery changing, it is significantly cheaper to buy replacements from your local Boots or similar, however the Suunto replacement pack does come with a new seal, so the choice depends on how much you expect the device to be exposed to water.