i made the switch on my old raleigh mtb a few years ago and it really does make a noticeable difference. unless you ride off road, suspension is really nothing but an energy suck and highly over-rated for street riding in my opinion.
i found a cro-mo rigid fork on ebay for around 30 bucks. it's pretty heavy, but my old raleigh is a 1" threadless so i was looking for a not all that common fork and when i found one on ebay, i snatched it right up.
here's my bike post-conversion:

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