You don't need $1200. I bought a brand new Giant TCX (cyclocross bike) last year on ebay for $700. Sold it last weekend after buying a Kona Jake (cyclocross bike) on ebay for $700.
Sadly I'm not fast enough nor could I compete with the "oldest" masters category we have here in Georgia - 45+. The oldest rider in that group is ~48 years old. I'll be 65 in a few weeks and have had knee surgery that prevents me from running and jumping. But if I was 42 like you - mr,grumpy - I'd be out there having the time of my life. As it is all I can do is cheer the riders on at the local races and have a blast riding my cx bike on the cross courses (the day after the races) and local mtn bike trails.

Why not give it a shot? You may like it.
BTW: some cx riders do ride on mtn bikes.
http://www.georgia-cross.com/images/...a/DSC_5889.jpg
http://i373.photobucket.com/albums/o...g?t=1259100292

I do not do CX-type competitions, but I love my CX bike. I like long fireroad rides with some singletrack and I do not drive a car to the forest, I ride maybe 10-12 miles on tarmac on a regular training ride. The CX-bike is faster than an Mtb on allmost the whole ride. Technical singletrack downhill sucks, I'll never be that good on a bike. With studded tires in winter it is also a much faster alternative than an Mtb (with it's much wider studded tires) when the roads are cleared.

Just thought of this comparison --

Cyclocross is to WRC rally racing as MTB'ing is to rock crawling-style offroading. The automotive equivalent of a cyclocross bike is a rally car (Audi, Citroen, Peugeot, etc) while an equivalent of a mountain bike is a Jeep or Ford Bronco.

Lighter, faster, tailor-made to the course they'll be running -- that's why cyclocross bikes are the way they are.

I think that helmet cam vidio answered it best. I keep hearing about all the mud and stuff but I think I was on a WHOLE diferent page all together.

watch this video

http://www.youtube.com/watch?v=H_W8AsilPMM

"Make a bike race as stupid as possible, and people will still do it"