Well I play with and without metronome. They are annoying, but as far as speed is concerned they do help you keep time. It's like a discipline use it and benefit it from and see results fast or take the freestyle method (which is to go without metronome) as see results slower.

I did managed to up the speed of some few scales I practice upto 20 bpms but that took like a month :eek:

If you do decide to get one.. get ones with percussive sounds not irritating beeps (like my one which I got in the beginning cos the local store didn't have anything else). In the long run you're ears will love ya. If not.. just download one off the net as least.