I like intervals. Honest. I normally do them twice a week and weights twice a week also. Throw in a couple of endurance rides done nice and steady and maybe the chaingang or a race which is the exact opposite (!) and that's my week. It can be pretty effective and doesn't mean huge hours in the saddle - ideal when you have a full time job and perfect training for 'cross.
I got switched on to this type of training a couple of years back by a good friend from Oregon, Don Leet. He writes a pretty neat and thoughtful blog at http://www.donssunnysideblog.blogspot.com/
Most of my intervals are 4 min ones at about 85% of your max hr. Usually 5 x 4mins with 3 mins recovery in between. You're teetering just below your threshold, not totally killing yourself, so the pain isn't so bad and generally ranges from comfortable (if i'm real fresh) to owww, this is hurting quite a bit, time seems to be standing still here (if not so fresh). The cool thing the warm up is only 5 mins and same for the warm down. A quick bottle of rego (sure they sneak something addictive in here..), some stretching after and you're all done in less than an hour! The idea here is you get a quality session in and recover quick so you can do more quality sessions sooner.
Problem is you have to be strict with yourself and do the endurance rides steady so your ready for harder training sessions. This aint always easy and also can make you a pretty dull person to ride with!! So I don't always stick too rigidly to it.
Do most of my intervals on the turbo. Turbo can be pretty hard on your head though. I think I've watched 'Transition 2' (US riders racing cross in Belgium) so many times I start talking american in my head. This isn't very healthy. So tonight with the lovely weather I got out on my mtb and did some intervals up Janets Brae, the forest road up in to Glentress Forest from Peebles. Takes about 5mins of climbing to get upto the top, then about 1min of descending down an ace bit of cheeky singletrack back to the start. I did 5 and by the 3rd time down the descent I was starting to get my lines dialled and collect a nice array of rambo style cuts (ok small scratches!) down my arms from the foliage..
I'm in the middle of an overload block this week, 5 interval sessions in 4 days. Tonight done means 2 down 3 to go. Dig in!