I walked Knighton to Prestatyn on ODP last year. Worked out around 100 miles. I plan to do Knighton to Chepstow next spring.
It was my first attempt at a long distance trail. I walked solo, camped all the way without booking anywhere. Had a brilliant time. My choice was influenced by: Easy rail access either end. Rail escape routes at Welshpool and Chirk if I wanted to bail out.
I averaged 12 miles a day for 8 days which was plenty enough for me. My longest days were 15 miles or so, over the Clun switchbacks and over the Clwydians.
I used the Trailblazer guide and read it backwards!
I made a little youtube video of my walk:
http://www.youtube.com/watch?v=raierOxeY9w [nofollow]I'd recommend camping because you're free with your schedule. If the weather is poor and you want to cut the day short, you can.
There were two guys walking at roughly my pace at the same time who I saw pretty much every day. They wild camped the whole thing and had no bother. I was happy to pay for campsites because I like a shower after I've pitched up. I was close to a pub pretty much every night. The only exception was the night before the Clwydians. The last proper campsite listed in my guide was Llandegla, but that left a long haul of about 20 miles to Bodfari with a bad weather forecast. I didn't fancy it. I considered wild camping but I called ahead to Gweryd Lakes, a set of fishery lakes, about 4 miles further on. The guy said they were new owners and didn't offer camping anymore unless you were fishing. Anyway I got chatting to him and he ended up letting me stay. The place was really beautiful and I was the only one there overnight once the last angler had gone home at about 8. I'd lugged a few beers up from Llandegla and had a marvellous times lazing by the lake getting a bit drunk and reading my book. The showers etc were excellent too.
Let me know if you want any more pointers.