I find an altimeter handy, but not essential. Given the choice of paying anything like the Vector's full price and not bothering, I wouldn't bother: a cheapish Casio with a backlight will tell you the time to a few seconds a month and the battery will last for ~ 10 years on recent models.
My altimeter watch was from Santa, and I strongly suspect he got it from F&T's bargain bin for £40, and the same model is there now for £25. See my review here. It's not great, but it's okay, the altimeter works, and it will save you a small fortune over a Vector.
I had the battery changed at a local market. You get plenty of warning it's running low before it gets useless so the virtue of a self change is a bit lost on me: I could probably have done it but compared to someone who does it 10 times a day every day I'd still be looking for the right jeweller's driver by the time they'd have finished the whole job and charged me some ridiculously low sum of money for not having to do it myself.
I have yet to see any of these watches I'd be happy to wear somewhere I didn't think the altimeter would be useful as they're all pretty chunky, heavy and clumsy. If I just want to know what the time is I use the aforementioned cheapish Casio (~ £20 at Argos) which is a lot more comfortable and interferes much less with cuffs and sleeves. Watches have been insanely reliable for little money for years now, there's no need to "invest" in something fancy if all you want is to know the time reliably, and the cheap end of the altimeter market will still be robust and reliable for not much more.
Pete.