I bought a CRM250 in Jan 2005 and have been very pleased with it. So pleased I bought another one in Jan 06. I bought one because they are acknowledged to be one of the best trail bikes ever built, but I had no idea what that meant at the time. Now I've owned one for 30 months and done some green laning, I know what they mean.
There are 4 versions of the CRM - the mk1, mk2, mk3 and Active Radical. For more details on the differences see crm250.com. They are all based upon a rather old motocross bike - the CR250. However, Honda made significant changes to the CRM and it's those changes that make the CRM such a good trail bike.
The main changes are to the engine. A motocross bike needs power and so the engines are designed to produce power up the rev range. A trail bike needs traction at much lower speeds and so Honda changed the CR's engine so it pulls well from low down. When you are climbing up bumpy and rocky tracks you tend to be going slow and on the edge of balancing over. You desperately need the engine to keep pulling and in a controlable manner. The CRM is a star. It will not stall; it just keeps going and going. It's also manageable. I've been out with people on large 4 strokes and race-bred 2 strokes like the KTMs and the CRM is often the only bike to make it up the big climbs. The big 4 strokes have too much torque - the riders wheelying into the bracken as the rear gets good grip on a rock - and the race bikes need more revs to work - lots of difficult to do clutch slipping - not what you want in this situation. Also, out and out power becomes irrelevant on a trail - you just don't have enough grip. If fact, too much power is a disadvantage and slows you down.
Another key feature of the CRM is reliability and starting. When you are in the middle of nowhere, you are very aware of the difficulties of having a bike that breaks down. Your bike is covered in mud and stuck in a bog, but you need it to start. Ask someone with a big 4 stroke how they like kicking it over in the middle of a big puddle when their battery is flat! Again the CRM just gets on with it. Also, it's relatively easy to rebuild your 2 stroke engine - not so with a race bred 4 stroke.
General handling is great on the CRM too. You'll soon find yourself thowing it about and spinning up the rear. Honda seem to have the capability to get the balance right on their bikes, which is such an important attribute. Comfort is also good. My mate has a KTM and he has a sore ass after 30 miles - the seat is a plank. Not what you want on a day out of trail riding, especially if you're carrying a rucksack. I wouldn't want to do any real road distance on it though, because of the position.
The only downside for me is that power on the road is not as impressive as the racing enduros. I would like the bike to wheely more easily on the power, but it does come up in second. But it's still very good fun in the twisties. I geared my bikes down a bit to get more life into them, which is a good idea.
When buying, look at condition first and how well the bike has been looked after. If it's been raced in enduros it will have had a hard life, but may have been well looked after too. Plastics are expensive, so people don't change them without good reason. However, any bike that's been used off road will be scratched a bit. That's normal. Check the engine is running quietly and that fork seals and wheel bearings are okay. Make sure everything is straight. I would stick to mk3s or Active Radicals as the suspension is better and they will not be too old. Most things are easy to fix and cheap, so it's not a bike that's a big risk. Watch out for extra costs like bearings, suspension parts.
Other bikes worth looking at for trail riding are the Honda XR400 and Suzuki DRZ400. KTMs and Gas Gas are good too, but much more suited to racing. If going down the KTM route, I would suggest the 200 and 250 2 strokes as being a better bet than the 4 strokes. They're all great fun though!